The Pats secondary is definitely a lot better. And the Ravens run-D versus the Pats new, powerful run game may very well be the key matchup of the entire game.
Still, I'm not feeling great about the Pats' ability to overcome the tough, physical Ravens D without Gronkowski to create mismatches.
They're going to have to do a lot of damage on the ground to open up the passing game, or else the Ravens will just jam Welker, Lloyd, Branch etc at the line and Tom will get frazzled.