You have to consider how close you will be to the screen, larger is not necessarily better. From too close up, your field of view is not large enough to really take advantage of it and you end up craning your neck all over to see. This is especially bad for FPS gaming as you can't take in your surroundings well enough. One of my clients had a 46 or 48in screen on a deep desk, one of those old large wooden 3ft deep executive desks. It was MISERABLE. It's nearly 3 feet tall, I had to look up waaaaaay too much to see the top and because it was so far away, they actually had lower the resolution to be able to see the text on it, especially near the top.
I recently had to replace my screens after one of my dual 25in died, and I actually paid more to get smaller screens because no one wants to to sell high resolution, in a smaller size. Why? Because it doesn't make sense on a desk. Humans have a wide field of view, and our necks are better at twisting than they are at looking up, so extra wide is fine, but too tall gets old really fast. Several times now I've had to use monitors that I found were actually too tall to be comfortable, the first was a 22in crt on a shallow desk, and the second was that customers TV screen, which even they said was miserable. When the son moved out, he took it with him and the bought a 25in.
OH, and something not mentioned and does matter, a LOT, is scaling.
Mac does this really well, but that's because it was engineered for a high res screen. Windows scales okay, the taskbar can get a bit small on Win8 or 7, 10 is better, but other than that most things on it seem to adapt to high res okay, not great, but okay. Browsers can be very iffy. Linux support for it varies depending on the desktop environment, for example Cinnamon does great at 1080p, and at 4k, but 2560x1440p screens are stuck in the middle and results in some rather small font (which is what I use). On the other hand, Elementary works great on 1440 and even better on 4k, but oh god is it horrible on a 1366x768 screen, the icons are massive.
Some of this can be fixed, some of it cannot so the best advice, go test drive one of these screens before you buy, because it doesn't always work as well as you think. Honestly, on such a large screen being so far away, lower resolution may actually be better and cheaper.