Relevant to this discussion, I have a new DR and I'm looking at purchasing either the Canon 28-135 IS or the Sigma 24-135. I hear a lot of good things about the Canon lens but I haven't heard much one way or the other on the Sigma lens.
The Sigma is 2.8-4.5 versus the 3.5-5.6 on the Canon. Plus the Sigma is a bit wider on the wide end and about $100 bucks less to boot. I'm much less concerned about the price differential than purchasing the right lens but I'm interested in opinions out there on which lens is best. Thanks in advance for your help.