WARNING! this is a huge file and might take a while to upload.

Wait for it to load both layers.

This is what Ive done so you can appreciate the difference.
Loaded both raw files in ADOBE CAMERA RAW (20D and 5D) as 17.5 MP images so both look identical in size and then cropped the center area from this shot http://www.pbase.com/sergio/image/71477045 .