I'm looking to pick up a new lens that would primarily be used for sports photography, mainly basketball and hockey. It is going to be used mostly indoors, so the wider the apeture, the better. And since it will be used for sports, it has to be a zoom lens.

I've heard that 70-200mm lenses are commonly used by Sports Photographers, so I've looked into two lenses that fit that category - the Canon f/2.8 with L glass (not the one with IS) and the Sigma f/2.8. Cost is an issue, but since will probably be trading in my digital rebel body to help reduce the cost, I would be willing to spend a little extra for the better lens.

What would the readers of this board recommend. I know the Canon lens is good - I see a number of professionals use it. But is there a huge drop-off between that lens and the Sigma one? Which gives me the best picture for my buck?