Agree about Manning being better than Brees, but you cannot say is that much better. Brees had a spectacular year (partly due to Bush being a lot better than Addai, but look at the difference in receivers).
The thing I love about the Bears, is that they don't need to blitz. Their D line is good enough to create pressure and they wear you down more than anything else. I think they will take the Colts' running game away early an force Manning to hang in the pocket and take hits with good coverege. The result will be based on whether or not Manning is tough enough. If he starts getting scared and throwing early, the Bears have a great chance of winning.
As far as the Bears' O is concerned, their line is a lot better than the ones you mentioned. That is the only reason they are able to run so well. Desmond Clark has been huge in that respect IMO. He is like another lineman in there. Did you see the block on the reverse of field run by Jones? Great awareness, great blocking and he had a few nice grabs. Kreutz is another huge factor. He is arguably the best center in the league and remember, that is who calls out the blocking assignments.
If the depleted Pats defense caused a few bad decisions for Manning, you can bet your ass that the Bears will do just as well. If Grossman gets off to a good start and controls possession, it could end up being a blowout in favour of Chicago. The Saints' defense is not worse than the Colts'. Granted Indy has been spectacular in the playoffs, like someone said before, form is temporary, and they did not show class during the regular season. And just because the Bears' defense relaxed a bit during the end of the season due to the fact they were so far ahead record-wise, does not mean they are not the best in the league by far.
I'm going to go with Grossman making some mistakes but the defense saving his arse as well.
Bears to win 31-27
vs.
