I'm going with Peyton, and it has nothing to do with me being in Denver (i'm a Bears fan).
My reasoning is based first and foremost with the fact that Denver is about to get a first round bye and will compete for a championship this year. The Vikings are fighting hard, but very well may still miss the playoffs. I don't see how a guy that plays on a bad team can win the MVP. What good is being "most valuable" to your team if your team doesn't accomplish anything?
If you take Peyton or AP off their respective teams, they both take a drastic turn in how good they are, but AP's team would still probably have the same outcome... missing the playoffs.
He very well may beat Dickerson's rushing record, so it's weird that he doesn't win the MVP, but I feel like you have to actually propel your team to be valuable. AP is his own MVP, because he is having a highlight year. It just isn't helping his team win enough ball games.