I can't speak about the Canon but I have the Tamron. It is an excellent lens, very sharp and pretty good focus speed. It doesn't have IS or USM and the focus motor is a little noisy. I don't think it is loud but some say that it is. The main reason I like it is the IQ. It is excellent!
Originally Posted by Shelly
Canon 7D - Canon 17-55 IS USM - Canon 70-200mm f/4 IS - Canon 50mm f/1.8 - Sigma 30mm f/1.4 - Sigma 10-20 f4-5.6 - Canon 430EX II Speedlite