By Hitoshi Doi (doi@usagi.org) My thoughts regarding the EOS 20D and EOS 10D are as follows.

Revision 0.7 (2004.09.30) Revision 0.8 (2004.10.04) Revision 0.9 (2005.09.04)

feature	comments
pixels	Going from 6.2 mega pixels (3072x2048) to 8.1 mega pixels (3504x2334) is only a 14% increase in size along each dimension, so it's almost unnoticeable.
AF (auto focus)	I only use one-shot AF with the very right AF square (top in portrait mode). I don't see that much of a difference in the AF speed or accuracy between the 20D and 10D. I prefer the straight AF point pattern of the 10D over the circular pattern of the 20D.
image noise	With the 10D, I tried to use only ISO 200 and ISO 400. Same with the 20D. The 20D's ISO 800 is cleaner than the 10D's ISO 800, but it's still no match for the 10D's ISO 400. But I won't feel as bad using the 20D's ISO 800.
shutter	The 20D's 5 frames/second is great for events. However it's too fast for portraits, as the flash can't keep up. It would be great if the 20D was able to switch between high speed (5 fps) and low speed (3 fps). Also the 20D's shutter is much louder than the 10D's shutter. This is what a shutter should sound like.
buffer speed	BIG difference! The most significant difference between the 20D and 10D is the buffer size and speed. The 10D's buffer is 9 shots, and 20D's buffer is over 20. The buffer also clears much faster with the 20D, as it can write to the CF while the camera is active doing other things. Because of the small and slow buffer, the 10D was limited to a maximum of 1000 shots per hour. The 20D can easily go over 2000, assuming there is enough CF cards. (I can take around 1000 in 20 minutes.)
buffer flushed	With the 10D, it was easy to tell when the buffer was flushed, because the image view would only work when the buffer was cleared. With the 20D, since the image view works even while the buffer is flushing, it's had to tell exactly when the buffer finished clearing. This is important when switching CF cards.
image view	There are good and bad things about the image view of the 20D in comparison to the 10D. speed The image view on the 20D is very fast. No comparison to the 10D. zoom The button to zoom in and zoom out is the same for both cameras. But for moving the zoom location, the 20D uses a small joystick and the 10D uses the wheel. Since I use the camera in portrait orientation with the grip, the joystick is too far away from my right hand. Moving the zoom with the wheel was easier.. but I think I'll eventually get used to using the joystick. type The 20D has three types of image view: 1) full screen, no info, 2) full screnn, limited info, and 3) histogram, all info. The 20D remembers the type that was used previously, and uses that for the image view. For the auto view after each shot, I prefer full screen, but when I view the shot with the button, I prefer the histogram. This was possible with the 10D, but not the 20D.
flash	Since I use the 550EXes in manual mode most of the time, I haven't tried out the new ETTL-II that much. It seems to work similar enough to ETTL that I can use it the way I have used it in the past.
AWB	The AWB seems to be very similar. Both are good outdoors. Both are bad indoors.
shutter	The 20D's shutter is supposed to last about twice as much as the 10D's shutter. Both shutters broke on me within one year, but the 20D's lasted almost 60,000 and the 10D's lasted around 32,000. So they were right!

There are probably other differences between the 20D and 10D, but since I usually shoot in M mode, one-shot AF, large/fine JPEG, the features that don't matter to me are not listed.

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