There are many reasons to buy a smartphone, but there are also many reasons not to. I normally don't like buying anything (save food) without doing a bit of research first. Some people buy for brand name, others because the color's "cute". And some buy because it's the newest, so it must be the best, right? Well, I am going to try to help you navigate through this; not just for megapixels and resolution but a few other things that will give you a level of confidence as to what you are truly buying.
Brand Name Shenanigans
Brand name means everything to some people, but to the savvy, it is just a name. What really counts is what comes with it. For smartphones there are at least two big names: Apple and Samsung. There are plenty of other Android phones (Samsung makes Android and Windows phones) like LG, HTC, Sony, or Motorola, but Samsung's fast adoption of Android has made it synonymous with the brand, and therefore good to pick on!
Apple does have a great smartphone, the iPhone, and it definitely deserve praise as they are the only ones to produce that phone. I have found the "geniuses" quite helpful, often doing things completely free of charge when possible. Great support is usually warrant of a great brand name. However, for example, they do lag on certain things hardware-wise. The only 1080p display on any iPhone is the iPhone 6 Plus just released, while Android phones are already passed that as of this year. WiFi has a new standard (passed N) named AC. The new perks of it are amazing, but iPhone only added this to their repertoire with the iPhone 6/Plus. Android phones like the Samsung Galaxy S4 and the LG G2 (last year's flagship models) already implemented the technology. The iPhone has also never budged from more than 1GB RAM, to keep this in perspective, many Android phones are coming with 2-3GB RAM. There are always the pluses such as being the first with 64-bit applications (which may or may not really help as I would consider the RAM an issue), retina display, and the iPhone 6/Plus has 128GB models.
Samsung on the other hand is known for a great deal of things: TV's, SSD's, and many household appliances. Their smartphones help put Android on the map, not to mention give the Samsung name further prestige. But if you dig a little deeper, the name may be the only thing to consider at times. I took a look at a first generation ASUS Nexus 7 tablet and a Samsung Galaxy Tab of the same year, and while the Samsung was around $50 more expensive, it's specs were sub-par in comparison to the Nexus. Do you really want to pay more for something slower? The only reason I could think of is for support, but I don't know anything about ASUS vs. Samsung support in the smartphone arena. When I had a choice between a Samsung Galaxy S4 and a LG G2 that was yet-to-be released, I didn't want to wait so I opted for a used Verizon Galaxy S4, which was still pricey. I got the phone and no more than a week later it was completely dead. No warnings or indications, as everything had been up-and-running, just dead. So I ended up buying the G2 a couple weeks later. This just goes to show while they do make quality products, brand name isn't everything.
I'll jump into megapixels now which takes some explanation. While most people think a higher megapixel means a better camera, not necessarily. The basic fact is that higher megapixels simply allow you to add more into a picture than lower megapixels. An example would be if you're trying to take a family photo. Let's say at 10MP (megapixels) you can fit four of five family members, but at 13MP (in the same spot) you can fit all five. That is to also say, that if you left the camera setting at 10MP, all you would have to do is take a few steps back in order to get all five. Conversely, a few step steps back with 13MP would allow you to get an extra person or two in the picture if needed. The only time a lower megapixel is a drawback is when you can't step back any further because of a wall or cliff edge!
With that being said, one 13MP is not the same as another 13MP (or any other size MP smartphone camera). There are plenty of cameras with the same amount of megapixels that are not considered equal. Case in point, the LG G2 has a 13MP, but so does the LG G3. I have owned both. While the G2 has a phenomenal camera, I feel the G3 does outdo it. The color feels a bit more natural, and upgrades to the hardware have helped do this somewhat. Another thing to note is that yesteryear cameras on smartphones usually have older camera sensors, meaning they should not be as good as the newer models. But what about different manufacturers with the same amount of megapixels? Well, there are plenty of articles comparing many different phone snapshots, and while many have the same megapixel count, there are obvious differences in quality. The difference doesn't lie so much in the camera sensors, as they are often the same. Where it does lie is in the post-processing by the actual software of the smartphone. The post-processing often tries to "beautify" photographs by attempting different tricks to make it look better than what it actually is. Sometimes it helps, sometimes it doesn't. This can make all the difference in low-light situations.
While most smartphones focus on jumping megapixels every year, iPhone's have not. They have been at 8MP for quite some time. I can only assume that they feel that people know about megapixel marketing myths and that 8MP is a solid amount to stay at. While I think it could use a bump, their camera sensors are great, and they definitely don't skimp on their accompanying hardware/software either. This just goes to show that even a lower MP smartphone does not mean it is worse.
One last thought on this is a smartphone's camera will NEVER be a replacement for a real camera, whether a handheld or professional-grade, it will beat out most any smartphone. Cameras are built to be cameras, which is why they have better hardware to support it and grant excellent quality.
Now for those into "hacking" your phone, Android is by-and-far king. Windows does have some developers making modifications, but not enough to be a potential contender. iPhones can be "jail-broken", which allows it to add additional apps and capabilities for free. But their biggest drawback is that jail-breaking is dependent upon what iOS version you have, as it usually takes a long time before it can be accomplished on newer versions. This is not to be confused with "unlocking", which is the process of unlocking an iPhone from a carrier to use with any carrier (with the corresponding networks) worldwide.
Androids on the other hand have A LOT of leeway in this arena. To start off, let's go over a few terms. Rooting is the ability to gain access to certain parts of the Android OS that users should not otherwise have. Bootloader is the system that helps boot up the Android OS on a smartphone (think of it like a BIOS or EFI in a computer). ROMs are custom-made Android OS files that can give you special abilities, UI tweaks, etc. Recoveries are special systems that will allow you to make complete system backups [Nandroids] and wipe cache and data among other things. There are currently only two main recoveries, CWM and TWRP. To put this altogether first you root a phone. Certain apps require root before you can use them. ROMs require root, and sometimes a recovery, before you can add them to your phone. Once you have been rooted, you can then add a recovery and/or a ROM. This may not seem like much, but you can flash files in recovery that can add apps, tweak and optimize settings, increase CPU/GPU power, etc. Yet, if this type of thing scare you, don't worry, you don't need to do any of this to enjoy an Android!
Not to forget, the bootloader needs to be hacked, bypassed, or whatever in order to allow a recovery to be put through. And that root often can allow for unlocking your SIM carrier, which is often done through the bootloader.
Screen Resolution Mayhem
Screen resolution does matter on TV's and monitors, and the higher they are the better they can look. On a phone, it may matter, but I argue that it does not always. If you think so, just ask a person with a smartphone that has 1080p, and a person who has an iPhone 6 or lower.
As mentioned above, I have the LG G3, the first phone to have QHD. In case there is any confusion there are a couple terms you might see being used incorrectly and interchangeably, like qHD, QHD, UHD, or 4K. QHD means 4 times 720p (which is considered High-Def along with the likes of 900p or 1080p). qHD means only a quarter of full HD (1080p). UHD means Ultra High-Def, which includes 4K, 6K, and 8K. There are some arguments in the definitions of using 4K and UHD, but I won't get into that here. Anyways, the LG G3 had the first QHD screen, and still has the highest PPI (Pixels-Per-Inch), but that shouldn't last too long...
The G3 does look phenomenal, but I can't say I'm overly impressed. My G2 looked great too, and honestly, if they hadn't improved the screen resolution and pixel count, there would be no love-loss. Beyond this, I also own a ZTE U950, which was purchased in China during the Galaxy S3 days. It actually contains the same CPU and GPU (made by NVIDIA) as the international Galaxy S3. What it lacks is a good camera, and a high screen resolution. I owned a Galaxy S3 and while the S3 screen was superior, the ZTE U950 is not unbearable by any means. While I would prefer a higher screen resolution, it in no way takes away from the smartphone experience.
Going back to PPI, you'll notice all screens seem to vary. There is no common standard. This changes from big-to-small depending on the screen resolution and physical dimensions of the screen. The Samsung Galaxy Note 4 has a QHD screen, but it has less PPI than the LG G3.
While some prefer the G3 because of its "truer" colors, others state the Note 4 looks better. This likely has to do with what materials make the screen for the most part. LG uses AH-IPS LCD technology, while Samsung uses Super AMOLED.
Speed and Power!
People easily get fooled by speed and power. This includes CPU's, GPU's, RAM, and Batteries. LG now has a special "step" battery design that allows it to fit more into its batteries, which logically allows for a little more power. But Samsung now has a special ultra power saving mode that can set your smartphone's color to grayscale when there is only 10% left, which will supposedly let it last for another 24 hours! I have read that the Note 4 does better than the older LG G3, but that the Galaxy S5 does better than the newer Note 4. I have also read that the Note 3 still has better battery life than the Note 4, but that the Note 4 can charge in half the time of a Note 3. So, what this all means is that you have to take it with a grain of salt. Tests can be done in a variety of ways, your usage is what matters. And, if you really just want a phone but the battery is holding you back, don't forget there are always accessories to add bigger or more battery power.
On top of this, most newer Android devices support fast-charging, which allows you to charge your Android phone in half of the time it used to. So, this could be a benefit to a newer smartphone, but there seems to be some that have successfully got older Android devices to enable this feature (at their own risk).
RAM is essential to any smartphone. I have noticed that lower amounts (obviously) just can't function as well ones with higher amounts. Bigger is normally better, but take the iPhone as the devil's advocate. They use 1GB RAM and they are efficient. In Android, it seems that bigger is always better. When I had the G2, 2GB of RAM was plenty. Now I have the G3 with the same amount of RAM (3GB is also available), and sometimes I wonder if I should have opted for more - although it could be that I use up too much storage space, which ideally should not be the issue since it comes with that storage space to be used...
Do faster GPU's make for a better phone? I don't know. I don't do any hardcore gaming on my phone, I have an Xbox 360 for that. If you get into the latest and greatest 3D-rendered games, it might be a plus. And sure it could help watching movies. But a lot of older smartphones have little to no problems playing most games and movies. While it may be a good thing to get that upgrade, I wouldn't worry about it too much. A smartphone GPU that isn't more than five years old, should be fine for most of your needs. However, this may become more important when UHD starts being pushed more. And if you are worried about the GPU speed, many Android phones have tweaks to increase that, but you'll need to get into "hacking".
What about the CPU? A fast CPU is great, and I really can't see a point to getting anything lower than a dual-core, if possible. Many apps are still created with a dual-core in mind, however, quad-cores have gained acceptance since their introduction. And the numbers? Well, faster speed is always nice, but for what? Maybe for intense games, but for the most part, there aren't going to be too many advantages with a faster CPU other than possible loading times. As with Android GPU's, you can usually increase the speed of a CPU to help combat those times when you just need to go faster!
Note: Increasing (and decreasing) the speed of a CPU and/or GPU can be dangerous and "brick" your phone if done improperly. This also goes for messing around with the voltage your phone uses for what speeds are being utilized. Even if done properly, there can always be side effects like overheating to be careful of.
Storage Space Situations
Many of us are used to having a lot of space, and this can be a big issue. iPhones, as noted above, now have an option to get up to 128GB. This makes a lot of sense because they have no MicroSD card slot. It could be a real pain if you were to use up all the space, or if you could only afford a model with less space.
Androids are better about this as just about all of them now come with a MicroSD card slot, but not always. The LG G2 did not come with one (unless you were in Korea), so you were stuck with what you got. The LG G3 did like the Optimus G Pro (the flagship model prior to the G2) and put in a micro SD card slot. There are not an abundance of Android phones that offer 128GB models, but they do normally offer up to 64GB. There are a lot of models, like the G3, that also allow for up to a 128GB via micro SD.
As I said in the beginning of this post, this information should allow you to be confident in making a "smart" smartphone purchase. There are many things to consider, some based on preference, some based on hardware/software specifications. The most important message I have to reiterate is don't let numbers fool you into thinking that a product is better solely because of them.