2560x1440 = 3686400 pixels
3440x1440 = 4953680 pixels
http://www.percent-change.com/index.php ... y2=4953680
It would be 34% "tougher" so expect 100 FPS averages to dip below 70. Or something like that anyway. Gsync helps with tearing, but there's no replacement for high FPS.
I used to own the Asus monitor that's somewhat similar to this, PG348Q with a 1080TI, and it was a pretty good experience. But 'downgrading' to a 2560x1440 at 144hz definitely felt smoother overall and no loss on resolution (just don't get the ultra wide viewing).