I've been thinking about selling my XSI and upgrading to a 50D or at least a 40D. How different are the controls? I see the scroll wheel but how quick is it to change controls (aperture, shutter speed) on the fly?
I know the 40D has less MPs and it's heavier but is it a "better" camera? My friend has a 40D so I'm going to mess around with it this weekend.
The main reason I want to change is that the picture quality seems so much better with the same lens on it (xsi vs. 50D). Once again, this isn't set in stone, I still have a lot more research to do and this is just me thinking out loud. I'm an amateur photog so I don't need (but wish I had) an mkII or at least a 7D

I Any thoughts?