Braun put up some amazing offensive numbers, but his defense was abysmal.
Tulowitzki's offense was above average, and his defense was amazing.
The way I look at it is which player would I rather have on the baseball team (not fantasy) that gives the team the best overall player to help them win games. For me it is a close call, but I think the ROY should definitely be Tulowitzki! He is one of the best SS in the game period and his offensive numbers continued to get better throughout the year AND more importantly, even as a rookie, he is already a team leader. The effort he puts forth every game and his overall attitude towards the game I think trumps Braun. Don't get me wrong, both players will have amazing careers, but Tulo is the choice!