I am no camera expert, but they look exactly the same except for one feature on the T3i (Eye-level SLR
with fixed pentamirror). The T2i only says with pentamirror. Considering the only function of this item is to transpose the image into the view finder I am not sure how important being fixed is. It may play into the durability of the camera, it may not. I also wonder if the T2i is fixed into position it is just not labled that way. If I had the money I would opt for the 60D rather than the EOS line. This gives you more RAW shooting options as well as a broader EV range.

. But if you are dead set on one of the two mentioned I would go with the T3i.
Brandon