Inherent contradiction there?
You can't go wrong at an M7 school - period.
You're going to be successful based on you - not the school you go to.
That's a fair enough statement. I guess my point was that rankings only give you a broad characterization of the school tiers - and within those tiers the schools you look at are roughly going to be the same, and the difference is more where you fit best, not what has the objective "best" ranking.
As for the other point - I've heard of someone turning down HBS for UNC - and being successful in his career afterwards. So the second point holds as well - its all about you. That being said - I'd think it'd be very naive to say that you're not sacrificing some quality in education/network between a school in the M7 and a school ranked in the mid-20s.