Ben is not as much a student of the game as Peyton. He also does not read defenses nearly as quickly. Peyton Manning is one of the all-time greatest QBs to ever play the game. If you can pressure him, you can rattle him. But, he gets rid of the ball so quickly that it is very difficult to do.
Ben is simply a different kind of QB. He is a great QB, but he likely will never posses Peyton's acumen. I'm ok with that.