Except that I just bought a XS last year, because that camera was supposed be such a big improvement (and it was). Gruber is of the opinion that the 11 has two big things going for it: battery and camera. I might not care much about extra battery life, but I do care about the camera. Not to the tune of another $500 for the upgrade, though. That's okay, the leather case on the XS is just now starting to look worn in.
I'm going from an XR to an 11 Pro because the 11 Pro is smaller, 5.8" vs 6.1"