Yeah it is hard to notice it at first but I find it is one of those things where once you notice it, you always see it then
I suppose it depends on the extended distance scaling option as well, mine is on zero but still, I never noticed it before the second last patch :/
Never used 1440P so can't really comment on it, what I will say about 27" 2560x1440 displays though is that they are better "overall";
- cheaper
- better choice of free/g sync (zero screen tearing, far smoother gaming)
- 144HZ thus better motion clarity
As for 21.9, it is great imo:
- You get more FOV at the sides in games e.g.
http://imgur.com/a/docX3
minecraft, 16.9 VS 21.9:
http://cdn.overclock.net/b/b3/b33e8221_o3Inygx.png
http://cdn.overclock.net/e/e8/e84265e9_D0QRMwV.jpeg
Most of my games support 21.9, the few that don't can be fixed by manually tweaking config files or using flawless widescreen. The only issue left is generally cut scenes/menus are 16.9 or/and the blood/rain effects will only show on the 16.9 area of your 21.9 screen i.e. you won't get effects on the right and left side of the screen
If you watch any films on the monitor then it is a must have, no black bars at the top and bottom, any films that are shot in 16.9 will just have black bars at the sides instead. There is only one type of film that is problematic for 21.9 screens and that is the imax as they switch from 21.9 to 16.9 throughout the film i.e. Nolan's films, you can get non imax versions for most films if you really want though and even when zoomed in, it isn't too bad tbh, quality is still great and most of the time, you wouldn't even notice that the film is zoomed in
23" 16.9
29" 21.9
21.9 just feels a lot more immersive when it comes to films & gaming imo.
I think if you are going for 21.9 these days, you really need to go for a 34" 3440x1440 screen though, unfortunately there isn't a great deal of choice, hopefully that will change over the next few months...