IQ are very close between the sony and canon, you are splitting hairs. The canon has the edge in higher iso as the A55 looses 1/3 stop of light because of the translucent mirror. But against the A580, the sony has a bit better noise control.
Canon is know for detail retention, so they accept a little bit more noise. The sony does noise reduction more, so it clips a bit more detail to keep the shot cleaner.
The T2i is a tried and tested AF system good for action. The new AF is very new, and seems to be very good. But AF system is just one part of AF system. The other is the lens. Get a faster focusing lens like a canon USM lens, and it is very faster combination.
Super Frequent Flyer, no joke. Ex Patriot and loving it.
Canon Eos 60D, T1i/500D, Eos1, Eos 630, Olympus EPL-1, and a part time Pentax K-X shooter.