Been running with the XS since Fri 21st and i came from an X. I can honesty say i can't notice any difference whatsoever. Not one. I was blown away when i went from a 7 to an X, but from an X to an XS, nada ! I know its faster, but in the real world, opening apps, or the camera, or facetime (which i was hoping was going to be faster, i can't tell) maybe i shouldn't of upgraded to iOS 12 on my old X a few days before, as that seems to have had more of an impact.
edit ** ok, so i thought i'd add one thing ! the changing of f.stop is nice in portrait mode. So not nada, but anyway, if you can get an X at a decent price, don't feel bad about it.