Both will work just fine. I think lenses are more importent then either of those camera bodies you listed when it comes to shooting sports. Now maybe if your shooting pro sports, frames per second would be a little more importent. I have some sports image (High school & college) on my home page attached to this reply. they were shot with both the Canon Elan 7 film and Rebel XT digital cameras.

I'd strongly suggest looking into a used 1D Mk II. I have a 5D, and got a great deal on a used 1D for a trip to Africa. It is MUCH faster to use than the smaller cameras. So if weight isn't a problem the 1D is where you want to look!