I think when I bought my 60D, the T3i was the then current Rebel model I compared it to. There were not vast differences between the two. They shared the same sensor and processor and major specifications as well, as I recall. The T3i was less money, slightly smaller and lighter, had a slower burst rate and I don't believe it had the built-in wireless flash controller like the 60D. I went with the 60D mainly because it felt more comfortable in my hands, a bit less cramped than the T3i.
Beyond that, I think that 90% plus of the time you'd have trouble distinguishing between shots from the two models.
