I’ve been asked quite a few times what makes an Xbox Development Kit different than a debug kit. The main answer is that the development kit is larger, and houses two additional addon cards that the debug kit does not have. I received an extra pair of cards with a recent shipment, so it was easy to take some close up photos of some of the markings, which you can find below. There have been some pictures of the cards on the net before, but you would be hard pressed to find many that are this close.
You can see the additional USB port, which is normally hidden on most DVT4 kits (but available on DVT3 kits), along with the connections to use the DVD emulator, along with some advanced debugging capabilities. Enjoy!