It's funny, I first read your question as best at being a candidate (campaigning, holding rallies, etc) vs. best at being a president....

The primary isn't over for me yet. I'm voting for who I think will make the best president without regard to who is best against McCain because I just don't know. Can't predict the future. Remember Kerry vs Dean? Everyone just kept saying Kerry is electable, Kerry is electable. I remember thinking, what the hell are they talking about? Which is what I think when I hear all that now, with a little more detail. You can argue it both ways, both sides are well-reasoned. But in the end, we just don't know. So why not vote for who you think would make the best president?