I think this game is going to be low-scoring like the four playoff games these two teams have played to date. Even if both offenses are efficient (as Denver has been in its two playoff games), neither side is likely to give up the big play and both offenses are likely to be establishing the ground game, resulting in a low number of possessions game.
I'm fascinated by Denver's O vs Seattle's D. Manning likes to line up his O and make the defense declare what it's doing (
as Chris Brown details in his article at Grantland).
Seattle's D usually doesn't try to confuse anybody; they put their corners on the outside receivers and play cover-3 behind it.
Both sides are used to being able to win one-on-one battles; it's entirely possible that early on we see one side getting the upper hand and the other side having to adjust and go outside their comfort zone on the fly.
Denver's D played really well against the Patriots last week despite being short-handed, while Seattle's O has been kind of suspect for a while. On paper, they should be able to put up points (Seattle was 8th in points scored while Denver's D was 22nd in points allowed) but I'm not sure it will be that easy, especially since they like to run the ball a lot (2nd in rushing attempts; 31st in passing attempts) and Denver's run D is stronger than their pass D (10th in YPC against; 17th in YPA against).