Originally Posted by
dulvariprestige
I think the biggest difference between the two is the price, a $1,000 for the canon, as David mentioned, he didn't notice between the two, I'm not sure if he meant in IQ or the extra 2mm you get with the canon, both lenses use 77mm filters and have quick focus drives, I've never used the canon, but I'm very happy with the sigma, I've used it on fast moving objects and never had any problems with focusing issues.