This is a game of powerful midfields. On the German side you have Ribery, Robben, and Schweinsteiger that are leaders on this team and their respective national teams. The magical duo of Xavi and Iniesta have been controlling the Barcelona style of ball possession since their current run of dominence has begun.
The real question is whether Bayern's defense and midfield can control the ball enough to take Messi out of the game, and whether Barcelona's defense is solid enough to hold the 5 midfield setup of Bayern and speed of Robben. There's no real advantage for either team unless they begin to control the game. To this end, Barcelona may hold a slight edge simply because their game, style, and deep understanding together.
G, Manuel Neuer
G, Victor Valdés