Canon EOS 40D
After first getting my hands on my 40D, I noticed how different it felt. The body is much, much more substantial in comparison to the smaller EOS 400D. The battery also lasts a whole lot longer. The camera's Autofocus system is purely excellent with its fast continuous focus which is essential for good birds-in-flight images. The body is constructed of a magnesium alloy and not only includes a 3" LCD Screen, but it has a display on the upper face of the body. The 40D brags a higher fps rate than its predecessors- at 6.5 fps, this is a big step up, and only 3.5fps behind the top dog, the EOS1DsMKIII.

Canon EOS 400D
This camera was my first digital SLR. Its great price and above average specifications make it a perfect camera for the beginner, and for an entry level model, the 400D is truly great. I've been using mine since August 2007 and through practice and lots of manual reading, it now feels like an extension of my arm. For want of prolonged battery life and the ability to use a shutter button when vertical shooting, I purchased the BG-E3 battery grip shortly after I bought the camera. The 3 frames per second I feel however, is not sufficient for capturing birds in flight.