[Bail]

There are differences where I would consider a 20D over the 400D.

- 400d can only do 1600ISO where the 20D can do 3200ISO
- 400d does not have a LCD control panel on top of the camera. You have the use the rear of the camera to make adjustments.
- 400d Shoots at 3fps. The 20D does 5fps
- 400D Has No Spot metering
- 400D has a 1/4000 Shutter speed where the 20D has 1/8000

However the 400D has something that I would love.
ICS (Integrated Cleaning System). Basically it shakes the filter in front of the sensor. I wouldn't call it cleaning but It will make so you won't have to clean as often as you would on a 20D.

IMO after trying both I would get a 20D over the 400D unless there is a reason you need all 10mp. I love the LCD Control panel on top of my camera. There are times where I dip into the 3200ISO. It's noisy but in the right situation (ie. Fast action, Low Light) it helps. Plus having big hands the camera fits me better. even more so when I use the battery grip.

Have fun with the 30D.