To TS, many other posts about this comparison already. There have been mixed reviews about the noise levels. I think what's more important is your budget. I mentioned this before that its not just the extra $400-$500 you have to consider, but extra lense cost. An 18-55 kit can work very well with the 40D, and I'm not saying it can't on the 50D, but just that you get the best out of the 50D with better lenses, and the starting point would definitely be the 18-200. So with the extra cost from the body and lense, it totals to quite abit. Something to consider.