Most will probably pick Serena, but I think Venus has been in better form. Venus in straight sets. IF it goes 3, Serena wins.
I think Venus's win at Wimbledon makes this less "life and death" for her. Serena, on the other hand, is probably hungrier for this title than any other person in the draw. And that includes Elena and Jelena, both of whom I think want this horribly, and yet still not as badly as the Fierce Stomping Diva. I think Serena in 2.