With a 1070/1080, you'll get better performances with any resolutions. You just get such a high framerate on 1080p that it's not useful with current games (a GTX 970 would probably already have 60+ fps).
(at least that's how i understood it, same thing that Buddy said)
But in the future, it might be useful if you keep your 1080p resolution. Plus, you can also superscale your resolution (make your GPU compute a 3840x2160 (4k UHD) and display it on your 1920x1080 display, it will look cleaner and sharper)