What sports?
The 5D, at 3 FPS, is pretty slow for sports. That's not its forte -- it's a landscape camera.
The 30D does 5 FPS so it would be better.
But, frankly, I strongly echo the other comment about getting a used 1D mark II. I have one -- its autofocus will blow both of those out of the water. It's not even a fair fight, and it does 8 FPS. If you want sports, the 1D mark II is the best camera in the world at it. Well... until the 1D mark III ships, that is :-)