I brought my 1D and the borrowed Rebel out to shoot some gulls. I found that I could obtain initial focus equally well with either camera but the Rebel was no match for the 1D when it came to keeping focus. I constantly lost focus with the Rebel but once the 1D locks on you've got it. The first two pics are with the 1D and the third is with the Rebel. The second one is cropped quite a bit which I usually don't do but at this small size on the web it will work.