While you are technically correct that the 20D has a smaller sensor than the 10D... they really are the same size.
The 10D sensor is 22.7 x 15.1 mm and the 20D is 22.5 x 15.0 mm, so the 10D's sensor is .2 mm wider and .1 mm higher.
A 0.1 mm difference is worth mentioning.
This is a trivial difference, and the images are better in the 20D. They are both "APS-sized." This difference is far smaller, relatively speaking, than the differences in images on 120 film for the same format size from different cameras.
Jeff Spirer
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