A 1070 does good in 1440p. A 1080 is a little more FPS and more future proof. I wouldn't consider a 1080ti for 1440p as its just overkill. Unless you need the FPS its always better to get something like the 1070 then when it no longer gets the FPS get whatever is out at the time at the 1070 level. I say that because a 1080ti is about 2x the price of a 1070 and in 3 years the latest version of the 1070 should be much faster than the 1080 ti. Me, I would get a 1070, possibly a 1080 or wait a bit to see what AMD brings to the table April-June.