Here's my radical theory: They're two different engines, each with their own strengths and weaknesses, and neither is truly superior to the other in all respects.

CE3 (or CE2, at least) has the capability to render just about every graphical effect known to man, and therefore can support more detailed, realistic environments than UE3. UE3, on the other hand, has the benefit of age and experience, having been optimized and tweaked as much as possible to squeeze every last bit of performance, if at the cost of detail. From the CE3 demo we had, framerates seemed to be an issue, and while it's an early stage of development, it's pretty clear Crytek will probably need to cut back a bit on the pretty if they're to make it smooth.

CE3, due to the nature of Crysis (and Far Cry, to an extent) also is designed to render foliage as realistically as possible, whereas UE3 has generally been confined to more static, lifeless environments. UE3's got the edge with urban and/or interior environments, as evidenced by Jean-Luc's screens, whereas CE3's a little better at large, open environments, as shown in the jungle comparison. The face one doesn't count, since the UE3 shot there is from the first Gears of War; the current build of UE3 allows for much more complex faces.

Personally, I'd wait until we actually see some games on CE3 before any opinions are finalized, but at the end of the day, both engines really aren't any better than the other at everything; while they trump each other in some respects, they also naturally fall up short in others.