I saw Steve Smith in London recently and have been a big fan of his for a while now. However, I do not believe in comparing him and Thomas Lang as they both have a different style and approach.
I saw both of them recently on the same bill, Thomas on a saturday and Steve Smith on the sunday. I also then went to another 3 Thomas Lang clinics.
Steve Smith has the very smooth flowing technique where he doesn't hit the drums hard, just as much as he needs to and in doing this can create some nice sounds. But Thomas Lang just blew him away. Not that I think he is better, as I said I just don't think you can compare them.
I think that deciding which one's dvd to buy is like deciding how you want to play. Both are different in many, many ways.