between the 20D and 30D, for a newbie like myself i think i prefer the 30D. the only reason for this is that the screen is larger and i'm able to check my picture and composition better after i take the picture. to me, it helps me learn a tiny bit better while i'm on the go. also, when i'm on holiday i prefer to look at a slightly larger screen when playing back pictures. just gives me a little bit more flexibility.
i also like the ISO 1/3 increments as it gives that slightest bit more flexibility.
but the differences are really minimal.
- larger screen
- spot metering
- selectable 3 or 5fps
- 1/3 stop increments for ISO
- direct print button
- slightly improved a/f (Canon did not say what was improved)
- picture styles
- body has been made slightly rounder