Well, about the 1 ms vs 5 ms thing; for FFXIV in specific, you won't notice the difference.
As someone who owns a 1080P 1 ms monitor and also this bad boy @ 1440P, however... I have to suggest you stay away from 1440P unless you plan to invest on a very powerful GPU/CPU.

I use a GTX 780 (Not the Ti version; bought prior to Ti being available -- still bitter about that!) and while it runs most games at 90 FPS or higher, some games will still bring it to it's knees.
FFXIV in particular does not; but keep in mind we're talking about a $500 USD+ GPU.
For crowded areas, it gets pretty nasty when you have that much being shown/process. Your CPU will also take a hit and hard.

Those are things to consider.
Personally? With your GPU I'd go for a 120 HZ monitor @ 1080P. You might not get 120 FPS on every game, but with a little tweaking on the graphics department, you can potentially reach it or get close to it.
Good luck, hope this helped.