The Giants have a phenomenal defense. It's what won them the Superbowl against the Patriots in the first place. they put pressure on Brady, and I think he spent more time on the ground than on his feet. I still don't think Eli is all that, he's a decent quarterback, but not a great quarterback.
As for the Pats, their defense is young, and it took them a while to gel. I think they'll hold their own just fine.