Yahoo의 digital_astro그룹에 올라온 글입니다. 한 아마추어가 매뉴얼 상으로 나와 있는 스펙을 비교했는데 300D에서는 여러 수동 기능이 빠져있다고 합니다.
단점 중의 하나로 메뉴 변경을 위해 들여다 보아야 하는 LCD 창이 카메라 뒤쪽으로 가 있답니다. 경통에 부착한 후 메뉴를 변경하려면 곡예를 해야 할 것 같군요. 타이머가 되는 콘트롤러도 사용할 수 없어서 여러가지 불편한 점이 많을 것 같습니다.
원문의 내용을 자신있게 번역하기 어려워서 원문의 일부를 그대로 올립니다. 양해바랍니다.

For some more differences (based on quick comparison of the manuals
of 10D and 300D):

- 300D manual is 140 pages, 10D manual is 184 pages,
- There is no Kelvin-based white balance setting,
- Metering mode cannot be set but changes depending on the shooting mode,
- It is not possible to set AF mode but it changes automatically depending
on the shooting mode,
. Flash exposure lock cannot be set separately but only part of AE lock,
- Curiously enough, estimated JPEG file sizes are clearly larger,
even though the resolution is the same (maybe they have changed
their measurement standard?),
- No high speed sync mode for flash,
- No separate setting of JPEG quality included in RAW,
- Exposure cannot be set in 1/2 step increments (only 1/3 step mode available),
- Receiver for wireless remote built in,
- There are two standard set of parameters (instead of one in 10D).

Overall, I'd say 10D is more rugged, has better burst mode performance,
has more flexible and easier setting of modes, is more customizable and
has better remote control.

For astrophotographers, 10D is better because:
- can use the TC-80N3,
- has mirror lock,
- LCD panel is at top,
- easier to change resolution (for test shots),
- has ISO 3200 (for aurora or other very dim subjects),
- can select the embedded JPEG quality in RAW images,
- longer burst possible (for planets and the Moon),
- metal body (more rugged and probably cools quicker).