Generally the extras on the TC have the wed features, the trailers, music video for whatever the big song is from that movie, a little feature on the "next" movie, a video game trailer and preview for the EE. But I heard RotK DVD won't have a EE preview, and a few behind the scenes stuff.
The extras on the EE are like 4 commetary tracks, lots more interviews with everyone, they go into more detail about why they did stuff they way they did, ect, and they usally have some footage from the premire of the movie. If I missed anything, please add too it.