I haven't heard football pundits mention either of these points.
1) Great offenses win by large margins. Great defenses win by keeping the score low, so great defenses will tend to win with close margins. They still get another one in the W column
2) Great offenses get worse in cold weather. Great defenses get better in cold weather. This is a familiar concept to football pundits. I've seen it mentioned several times to explain why record-setting offenses tend to tail off by the end of the season.
The obvious counter-argument is that the 3 top NFC teams are all warm-weather teams: SF, Seattle, and NO. There isn't even much chance of a cold-weather game in the playoffs for them, like Miami or Indy would have to deal with in the AFC. The only good cold-weather team in the NFC is Green Bay...maybe they have a chance to force a few Lambeau playoff games.
But the most important point is that the passing game, particularly the intermediate/long passing game, suffers in cold weather. And on top of that natural cold-weather decline, Peyton Manning has battled weak right-hand grip since coming back from surgery...a weak grip that gets worse in cold weather.
Like games played on Nov 17th and Dec 1st.