Neither side has any reason to be particularly confident. Peyton is the undisputed best ever regular season QB with a record of post season mediocrity and poor performances in cold weather, whose one and only super bowl victory was against the Rex Grossman-lead Chicago Bears. The Seahawks have been damn near unstoppable at home but outside of Seattle they've just been above average, and untested (but overrated) Russel Wilson on this big a stage could easily fold like a lawn chair.
There are so many possibilities in this game that I think only a fool would make definitive predictions.