While I agree that Tito would be very valuable to the pro wrestling industry, I still agree with him that he still has three more years left of MMA in him. If he goes on to EliteXC, a place with MUCH less competition at 205 than what the UFC currently has, I can see him becoming even more of a star than he currently is, and I see him ending his awesome MMA career on a high note, rather than leaving the sport after his lost against Machida.
As far as which wrestling company he would benefit more from, TNA or WWE, I have to say WWE if for short term, TNA for long term. Tito would never want to deal with WWE's road schedule, but I could see him loving to perform at a Wrestlemania. As far as TNA, if Tito were to enter pro wrestling seriously and want to make a big star of himself in the biz, I see him being more attracted to TNA since he would only have to work once a week and the pay would be great.
In the end though, I only see Tito doing something short term in pro wrestling (like either a Wrestlemania match against someone like Cena, or a program against Kurt Angle in TNA), and I don't see it happening until a few more years down the line. I think he's more interested in becoming a movie star more so than a pro wrestling 'superstar' anyway.