This is likely a topic covered plenty of times, and as such I won't make this a too in-depth article, but I feel it's something always worth reiterating and remembering that no matter what distribution of Linux (or GNU/Linux if you prefer) you use... it's all Linux.
You only have to whiz around the internet in message boards, YouTube comments and the like in regards to any Linux topic and you'll probably come across a "distro war" often enough. It can happen easy enough - someone mentions their distro of choice, someone else then mentions theirs and then comparisons start. From there, with personal experiences being shared, which quite frankly can differ quite a bit depending on one's hardware, software choices (or sometimes even luck) a discussion can quite quickly descend into a flame war over 'my distro is better than your distro'.
It isn't really something that's limited to Linux distributions or even Linux as a platform at all. It can happen on the internet with any topic regarding some sort of product or item. PCs versus consoles, consoles versus other consoles, cars, web browsers. The list goes on and on into pretty much anything you could think of.
I'm quite certain if you did a search for a forum on lawn mowers you would find an argument somewhere with members fighting it out over which brand of mower is best. Or heck maybe even toilets! You get my point.
So while it's something that will always happen due to the nature of the 'net, and well, humans, it's still worth bringing up the point sometimes that at the end of the day, regardless of which distribution we choose to use, it's 'all Linux'.
It's a positive point and I feel a realistic one. The fact of the matter is, many distributions will be running very similar or common underlying programs and libraries. The GNU stack of software is obviously an important example. The Linux kernel itself should go without saying. With the propagation of systemd, even init systems are very common nowadays but even with the distributions that use something like sysvinit or OpenRC, the average user certainly won't notice much difference. And of course when it comes to typical desktop applications, most of the very popular selections will be available on distros that are intended for such usage.
The main difference between Linux distributions will generally be simply software versions (for example 'stable' versus bleeding edge), available software selection in the mirrors provided by the distribution's maintainer and of course a little thing called philosophy. A distribution's philosophy, for example the choice to ship non-free software or only free software, may influence people's decisions on a philosophical level but from a practical point of view, will again influence the available software selection for download in that particular distro. Smaller differences will be things like branding/customizations to the desktop environment and general configurations out-of-the-box.
Obviously combinations of certain software and system library versions and particular configurations DOES mean one Linux distribution may work well for you on your computer, while another might actually fail miserably. Some people may then think that the failing distribution "sucks", but one needs to consider that for someone else with different hardware or choice of drivers may have completely the opposite experience. This of course is where people can then start arguments over which is best.
Some will argue that, from Linux as a platform perspective, that this is the problem with having so many different distributions and 'a lack of standards'. Regardless, the Linux ecosystem is a very diverse one and the sheer freedom which leads to so many "choices" is both a strength and weakness, but it is what it is. If you love what Linux has to offer, you may well have to do a bit of 'distro hopping' to find what works best for you.
As of this writing, my desktop computer is running Arch Linux with the MATE desktop while my laptop (and travel companion) next to me is running Ubuntu GNOME 15.10. They would be considered completely different distributions and certainly have differing goals when it comes to their average userbase, however I can say that on both machines I am running very similar overall software. Such as Firefox, Vim, Steam, Filezilla, Xampp, Blender, GIMP, LibreOffice, Transmission, VLC and PlayOnLinux just to name a few. They would be even more similar if I chose to run GNOME on Arch as well but ironically my desktop (until the next upgrade) has fewer resources to spare than my laptop.
But really, two very different distributions that I use pretty much the same core applications on and do very similar activities. Both run well and rarely ever give me any trouble.
I chose Ubuntu for my laptop because of, for the most part, less daily updates and a little more 'hands off', in theory meaning as a portable machine there's less outright updates to deal with, less downloads and should just work. I love Arch Linux for my desktop for it's 'hands on' approach and generally always having the latest in the way of software and drivers and I can customize to my heart's content.
Is one distribution necessarily greater than the other? I don't think so. And that's my overall point: it's all Linux underneath and I simply use whichever distro I feel works best for my needs, on any particular machine. In my opinion, that's a good mindset.