If you really look at this game they are both very close to being equal in a couple different ways.
#1 and #2 Defenses in the NFL (Steelers are #1)
Elusive Quarterbacks (Ben is harder to take down due to his size)
I think the advantage goes to Pittsburgh for two reasons.
#1 - I think that Pittsburgh is going to have success running the ball where Green Bay probably will not.
#2 - Most of the team has already been there, done that (a couple times) so there shouldn't be a question of nerves getting in the way.