Well, it shouldn't matter what brand it is with regards to good pictures right? But from the commercial point of view, with such a large user base from Canon, 20D should be the like what Amfibius mentioned:"the 20D will win by a country mile". Both are good camera.
"As mentioned, the 20D has been reduced in size over the 10D and previous models in this line from Canon. Such shrinkage is not without its price though. It has been achieved by reducing the size of both the pentaprism and the instant return mirror. This makes the viewfinder a bit dimmer and a bit coarser than the previous generation. The coarseness isn't all that apparent indoors or under low contrast outdoor light conditions, but outdoors on a bright sunny day it's painfully obvious. (Canon claims that the coarseness to aid manual focusing, but that's just marketing BS; simply an attempt to turn a deficiency into a feature)."