Let's get real here, and let's start by analyzing common opponents here. Sometimes this is a meaningless stat, because things do change from game to game, but it's a logical place to begin.
The Saints played a physical game against the Bills on the road and manhandled the team, 27-7. We all know what happened with the Bills and Pats, no need to rehash that.
The Saints handled the Jets, albeit in a tough game, 24-10. Brady and the Pats were basically clueless against the Jets pressure style D and the New York crowd.
If you are truly being objective, you have to say that the Saints clearly have the edge when it comes to common opponents.
Now let's look at matchups. Saints #1 offense against Pats D:
How in the HELL are some of you rationalizing the Pats slowing down an offense that has hung 48 on the Eagles and Giants? My analysis here is simple. The Pats flat out cannot pressure the QB. They are #23 in sacks. If you can't pressure Brees, you are done. Finished. Analysis doesn't need to go any further than that. The Saints can run 55 pass plays and 1 run, and you STILL will never come close to stopping them unless you can pressure Brees.
Shockey, Lance Moore, Colston, etc. etc. etc. match up bigtime against even extremely talented secondaries, and the Pats do not have an extremely talented secondary. I'd give the Pats a chance to game plan and slow down the Saints and possibly steal this game if it were at home in the N.E snow, but it's not. And you all know that.
With that offense, that crowd, and that revamped pressure defense, 49-20 is a very objective score. Hey, maybe somehow someone missed something and the Pats are really superior to the Giants. Maybe they will fare better in the dome. I don't see it.