as far as practicality goes, I'm quite jealous of my friend's 1440p monitor. gaming will look a little better than in 1080p, but it will take a lot more power ( akin to an R9 280x's) to run smoothly. My friend uses a 7970 and that is sufficient to keep a good framerate. It is a lot easier to place and deal with one monitor, but if you frequently work with spreadsheets or programming environments, it may be more practical to get the 3x 22's.
As for which is "better"... that's entirely up to you.