The dvd gives a BUNCH of Video Tutorials on how to use UnrealScript, make maps and mods. Also it has only one disk to install istead of alot more with the cd version.
First of lets make sure everyone knows what they are talking about
CD Version: Nothing sassy, 4 CD's (could be 6, not too sure)
DVD Version: Nothing sassy, 1 DVD
Special Edition Version: U-Script tutorials, UnrealED Tutorials, etc. A lot of sassy things, the ECE bonus pack is also intergrated. All the ECE is is a large patch that Epic made, adding new vehicles. (including player made MODS, they however can be downloaded off the web)
The only REAL difference between the game formats is how long it takes to install. All the extra stuff can be downloaded.