I don't perceive any difference in performance. I don't know if the AF tracking for action is at the same level, but I never use that so I'm a poor judge anyway. Face detection seems similar to me, pretty decent but not up to Olympus. I'm personally very happy with the EVF of the XE2 unless I'm using it back to back with the XT1 (which I do sometimes) and then I'm VERY aware of the difference, which favors the XT1 by quite a bit. And I really like the flip up screen. But I prefer the EVF location on the XE2, so if I'm going out with one body and don't take an ultra-wide lens (which is when I usually us the flip up screen), I'm more apt to take the XE2... I also like being able to save ISO configurations in the custom settings on the XE2, which you can't do on the XT1...
-Ray