MethU goes 46 years and sniffs a conference championship exactly twice in the Big 8/12 (and got absolutely crushed by OU) and within 2 seasons they win the SECE and play for an SEC championship. The only reason MethU even won the Big 12 North was because Snyder and Gary Barnett had exited the building and Gary Pinks was starring across the field at Bill Callahan, Ron Prince, Dan Macarney and Mark Mangino.
aTm spends the majority of their Big 12 existence getting rolled more times than not and within two years they're torching SEC teams.
missouri played for the SEC title because of a favorable conference schedule and a barrage of injuries to georgia and florida.
aTm has yet to finish higher than 3rd in their own division... yet they were still good enough to absolutely crush oklahoma in the cotton bowl... which should tell you that aTm is not the same aTm team from the R.C. slocum days.
seriously... if the big 12 is right there with the SEC... then why do zero members of the current big 12 have a win in the cotton bowl over the last decade when the game matches up teams of similar rank on an annual basis?
Maybe OU didn't want to be in the Cotton Bowl two years ago (I mean that's what MethU fans said about Bama in the Sugar Bowl). 
Plus, did I not say the SEC was top heavy . . . and yeah, Big 12 teams don't have injuries and such? So a few injuries and suddenly MethU who hasn't put a trophy of significance in the trophy case for nearly five decades wins the SECE and plays for the SECG.
Also, nice job by the SEC in ensuring that certain schools will have an easier time. I mean really, how can you even get excited about some SEC schools if their shadow isn't going to cross the threshold of your stadium but once every 8 to 10 years?
did i say big 12 teams don't get injuries and such? no. the number of injuries to georgia and florida, especially at key positions, was far and away above average. like, a couple of standard deviations above average. and yes, missouri had a favorable conference draw.
that isn't to say they weren't the best team in the east... they may have been. but they also benefitted from quite a few unusual circumstances.
and who cares about what they did for 50 years in the big 8? that has no bearing on what they are doing now. it's pretty funny that you think missouri and texas a&m have taken the sec by storm when their conference record was 19-14 over the last 2 seasons. and those were seasons where they were better than their average big8/12 years. and all you have to do is look at what they each did in the cotton bowl to see that.
it's comical that you think teams that change conferences, get a whole different recruiting base, new coaching staffs, etc. can't radically improve (or decrease) their standing.
each of those teams proved on the field by beating teams near the top of the big 12 that they were not some bottom-feeder teams.
and by the way... how does it feel to be virtually eliminated from the playoff before the end of september?