I think at this stage it's still ultimately between Webber and Hamilton, but it wouldn't take much for that to change. Webber has been on great form this season, and Hamilton has for the most part been fantastic - very few mistakes, yesterday excepted. Webber is also starting to push RBR towards making a decision on whether or not to back him, and whatever McLaren claim, if the gap between Hamilton and Button opens up again I don't believe they'll let them race each other if the situation arises. They don't want 2007 to happen again.
IMO we need to see more from Vettel, Button and Alonso before they look like they're really back in the running.
Oh wait, I just realised I haven't actually given an answer.
I'm going to go for Hamilton for WDC, but RBR may just edge the WCC. They should have walked it already, and there are more tracks coming up that should suit their car.