I think from a team strength standpoint, the choice would be SaxoBank. With the loss of Sastre, they don't have a true GC contender. Some may say the Schlecks but Andy wilted during the TT at the Tour. You have to be able to be a half decent time trialist to win the Tour and Andy hasn't proven that yet.
Team Columbia would be a decent choice too given Big George is there and we all saw how bad Kim K did as the GC contender. But in all of the Postal and Discovery years, Lance never had a big sprinter because he wanted teams that can help him in the mountains. So where would Mark Cavandish fit in this approach?
I know there is the whole American team connection thing too but Astana isn't an American team. Plus I can't see Contador roll over for Lance.
If I were Lance, I would have stayed retired. But if I were Lance and coming back, SaxoBank is loaded and gives him the best chance to win.