Thanks and glad I could find the club. I'd been told about it previously, but not with dashes between the words in the URL.
I'm really torn. I plan to use the lens primarily for inside at the tank (on a tripod most likely), but would like to do some outside macros, too. I just got a 70-200mm f/4 L IS and love it for outside shots. My wife is a bird stalker, so I thought it would come in handy. Once outside, though, there are too many nice thigns to try to get a shot of
. If camera shake is that much more noticeable on the Sigma, I may need to try the Canon. My wife has a hard time holding the camera still for shots. The extra weight might be too much for her, too (though, like I said, I'll be using the lens primarily). Decisions decisions. Since it sounds like the Sigma might work on the 1.4X canon extender, that is a plus for Sigma. I have a 25mm extension tube (EF 25II), though I haven't found it very useful yet (helps a bit when trying to take tank pics with the 70-200, though).
Thanks for all of the input. I want the better lens (don't want to buy twice), but want to make sure the little negatives aren't enough to make the better lens worse in the long run...