I'll second that.
Your point is extremely valid: a team's record at one point in time doesn't necessarily reflect how they were playing at another point in time.
It works both ways. The Pats got hit by the Jets, Ravens and Broncos when all 3 teams were hot. But the Pats caught the Titans when the Titans were in disarray. Pats should still beat the Titans, but they're a different team than when we played them. New Orleans faced the 3-0 Jets when they were hot, and the 5-0 Giants when they were hot, and trounced both. Just because both teams have struggled since then doesn't take anything away from the Saints' accomplishment - they soundly beat 2 teams that were playing extremely well going into those games.
I think it's fair to say that the Saints have played some very weak teams (Lions, Rams, Bucs). But Pittsburgh lost to Oakland last week, and Cincinnati lost to KC.
Overall, I agree that "strength of schedule" is meaningless. I wouldn't put any store by it.
The matchups should be nice. The Saints defense is very average if you measure it in terms of PPG (14th), YPG (17th), rushing YPG (20th) and passing YGPG (15th). But it's exceptional if you look at turnovers created (1st), points scored by the defense (1st), opposing completion % (1st, 53.2%), opposing passer rating (1st, holding opponents to a 57.8 rating, largely because of all of the turnovers and completion %), and red zone defense (5th). So the yards and points are somewhat deceptive. The Saints give up yards and points, but make big plays and turnovers, and score points off of their defense. The Pats will have to avoid mistakes and turnovers, which they have done well this season, ranking 2nd in turnover differential (the Saints rank 4th). I'd like to see more running and play action, and less shotgun.
The Pats defense matches up very well. 6th in YPG and passing YPG and 2nd in points allowed. 3rd in turnovers created, 3rd in opposing completion % (56.0), 4th in opposing passer rating (73). The big concern for the Pats is their ability to get pressure on Brees, and the ability of their 15th ranked rushing defense to stop the Saints' 5th ranked rushing attack average over 153 YPG. But I don't think the Saints have faced a defense as complete as the Pats' this year, nor one as physical. The Pats have faced fairly stiff defenses in the Jets and Indy, though they haven't faced one which makes as many big plays as the NO defense. The key for the Pats on D will be to stay aggressive and physical and not be afraid to give up the occasional big play. Play BBDB and the Saints will carve us up.
I actually think that the biggest advantage that the Pats have over the Saints is that we played Indy 2 weeks ago. We've already been battle tested against (and burned by) one of the greatest QBs of all time, and while the Saints' offense has more diversity than the Colts, I don't think our defense will wilt after having been tested by Manning and company. On the other hand, I don't think the Saints have faced an offense remotedly comparable to the Pats so far this year. It will be interesting to see whether they're defensive scheme continues to make key turnovers, or just gives up too many yards and points to the Pats.
At any rate, both of these teams are capable of winning the SB, regardless of who wins next week.