The Giants have committed 41 turnovers during the season. Mostly Eli Manning throwing interceptions. That is way too many turnovers and just puts too much stress on a team's defense and special teams. Eventually they crack. Which is why the Giants are not in the playoffs now, and will need help from the Bears to get in.
The Jets have significant parts of their football team disappear for long stretches. Sometimes it's the offense and inconsistent QB Mark Sanchez. Sometimes it's the defense, giving up way too many points and yards. The Jets are in, but in real danger of losing in the first round. I do think the Chiefs would be a real challenge for the Jets, especially at Arrowhead.
The class of the AFC is without a doubt the Patriots. The best of the NFC may be the Falcons, Saints or Eagles. They are a little bit closer together than the AFC, where New England is clearly the class of the league.