Last updated: November 2016
One thing that has bothered me for a long time about various laptop and desktop computers is their size. In the desktop world, there is not enough variance, and in the laptop world, there's too much variance. Let's start with desktops.
Why are the majority of computer custom-builds full ATX size, and why do the majority of the products have to be manufactured in this size? As terrible as they may be considered, most pre-built brand-name computers have been in Micro ATX size since 2003 at the latest.
Let's have a history lesson.
In the beginning of computers, the motherboard didn't do much at all; all hardware was a separate piece from the motherboard, and thus, the motherboard was hardly more than a backplane. Because of this, even the most basic functional computer needed several cards connected to its motherboard to be functional, so it needed to be big, in order to accommodate all of those cards.
Over time, more and more components became integrated into the motherboard, such as processor cache and hard disk controllers, which reduced the minimum amount of cards required in a functional system. In 1985, the Baby AT form factor was released, which shrunk motherboard size.
Then, in 1995, ATX was introduced by Intel. ATX was a huge step in the right direction; AT only permitted one rear-accessible port, and that was always the keyboard port, while ATX allowed any sensible number of rear-accessible ports, chosen by the designer of the motherboard. This was a breakthrough for component integration, because now any ports that the motherboard designer chose could be in the back. The motherboard size, and thus, the computer size, also shrunk once again.
In 1997, just like how IBM introduced a smaller version of AT, Intel introduced microATX, a smaller version of ATX. As much as it makes sense, microATX is compatible with ATX; microATX motherboards can be installed in ATX cases, but the opposite is not possible, due to ATX's larger size. In a matter of a few years, as previously with ATX to AT, microATX largely replaced ATX's usage in pre-built, brand-name systems.
This is where a split was formed.
Even though the overwhelming majority of home computers were pre-built, brand-name systems, many people still prefer custom-assembling computers to buying them pre-assembled, which is a good thing. However, likely due to the fact that many people wanted more powerful hardware and better components than a pre-built computer comes with, most of these people continue to use ATX, even to this day, in late March of 2016.
Because of ATX's popularity in the custom-built computer world, the biggest computer case selection is in ATX sizes, and the biggest motherboard selection is, as well. This caused the recursion of popularity; "more motherboards purchased are ATX, so we'll keep making ATX boards" "more motherboards are in ATX size, so we'll keep buying ATX boards".
However, even if ATX has a larger motherboard selection, there are still plenty of good motherboards in microATX size today, moreso than ever in the past.
In the past, ATX was essentially a requirement if you wanted a well-capable system. Now, thanks to component integration, depending on what we define "well-capable" as, it's possible to have a well-capable system without a single card in the system! It's also even possible to run multiple graphics cards in CrossFire/SLI (the definition of the word "impractical") in a microATX case, and even that isn't new!
As long as you set it up right, and aren't using extremely hot hardware, microATX won't give you any problems with cooling, either. Just set it up right, maybe even buy a couple of good 120mm PWM fans, and you're all set.
With that having been stated, it's pretty fair to say that the only systems that really, and truthfully need to be in ATX form factor, would be workstation systems or systems with very powerful graphics solutions, needing things such as many networking controllers, disk controllers, two or more high-power video cards (say, >175W TDP), and/or lots of hard drives. Those are absolutely valid scenarios requiring the use of ATX, although the necessity of these systems as a whole is limited.
Any usual single-GPU system today requiring very little or no extra expansion cards has no valid reason to be made in ATX form factor.
"But what's the point of building a computer inside of a shoebox?", you say. Well, let's look at the flipside; if you're fine my my Gateway 510X from 2003 being less bulky than your system, then suit yourself! Nobody said that you have to agree with me. Personally, I think you might as well be building a Baby AT or full-size AT system today if you insist on using such an aged and oversized form factor.
Laptops have so many varying sizes...too many. The most well-known and popular form factors are fifteen-inch, and seventeen-inch, the former being the most common. The thing is, once you go past 14", it's too big.
Fifteen-inch laptops are my least favorite form factor. People say that "it's the best of both worlds", but I believe it's the worst of both worlds. How come?
It's simple: It's too big to be small (portable), and too small to be big ("desktop replacement"). If anything, I'd certainly classify fifteen-inch laptops as a "desktop replacement" much easier than as a portable machine, holy moly, would I ever.
Even worse are 15.6" laptops. Fifteen-inch laptops are just too bulky, but 15.6" laptops are not only that, but I think they're also ugly. How come? I just think the resulting extreme width and short height from the aspect ratio in combination with the screen size is just plain and simply ugly.
There's at least the advantage that 15.6" laptops are the smallest form factor that can accommodate a number pad, but with the bulkiness and starvation of vertical space, you might as well get a 16:10 seventeen-inch laptop.
Instead, I suggest that we all should focus on the underrated twelve-inch and fourteen-inch form factors, and leave everything higher as a "desktop replacement". Twelve-inch for people who wanna move the thing around a lot, fourteen-inch for people who want the same thing with a bigger screen, and, if you want anything larger, it's time to give up portability, because fifteen-inch and higher is just plain unwieldy.