As a quick way to visually see how the final 4 teams have performed, here are their performance charts.
New England is #1 for a reason, they've had a lot of good results. I've had a few folks say they think even so, they are underrated, and what is holding them back are a few bad results. The Arizona and early season Baltimore loss don't count that much now, but the 49ers loss and narrow win over Jacksonville are holding them back a bit now. If you don't include those considering them aberrations their last 5 games have all been in the 90-100 range, very strong.
Baltimore had a tough patch late in the year, but were banged up a bit and perhaps the Cincinnati game didn't mean much to them. Ignoring that game, 3 of their last 4 have been in the 90-97 range, also quite strong.
Atlanta won a lot, but played a weaker schedule. In fact, they've only had a few results over 90 late in the year, their best again the Giants. They certainly don't look as strong as the AFC teams unless they can repeat their peak form.
The 49ers have also been a bit up and down, but like the AFC teams their highs have been in the 90-100 range and they've had a bunch. They look a bit stronger in general than Atlanta and are ranked higher, but they have to go on the road.