Okay, I'm going with Rogan on this one. He's been around the UFC for quite some time, and he obviously got quite a few contacts and offers to train with some of the best. Even if you listen to him commentating, he knows exactly what the fighters are trying to do and describes how they do it. "Oh shit, he's setting him up for a komora."
If they were to fight, it would go to the ground and Rogan will win by submission. Trust me, "Blade's" high flying acrobatic kicks will be nice eye candy, but who the fuck does that in the UFC nowadays? Yeah, he's got a lot of different styles under his belt (although all very similiar), but who the hell will try to do some capoeira in the fucking octagon?! I remember in the beginning days of the UFC, they tried to pair different styles against one another like: Kung Fu against Greco Roman Wrestling. (we all know how that turned out) Rogan I'm sure knows that Snipes could take him standing, so I really don't see him agreeing to a fight without having an edge (submissions) as well as a lot of help and strategy from others in the UFC.
Plus, lately, Rogan's put on quite a bit of size. Granted, Tae Kwon Do isn't a very good fighting system. Anyone can get a black belt in under two years. However, I'm definately not convinced that Joe hasn't done a very good amount of ground work given the people he knows in the Octagon.