First off, I'm not even an SEC shill, but I've taken a keen interest in the conference hopping that's gone on the last couple of years and while I'm sure Mizzou and Aggies fans alike think they'll make an effortless transition into the SEC, I don't think the numbers will back that one up.
Don't believe me? Roll the tape...
Since 1998 the SEC has gone 31-18 against the Big 12, and despite all of the debate about offense vs. defense, when the proof's in the pudding, the SEC always seems to come out on top. In 2003 and 2009 the BCS title was decided in SEC vs. Big 12 matchups and the SEC walked away victorious twice.
Regardless of what you think of the BCS system, the truth is, in title game matchups it's largely a function of getting through your conference undefeated if you're in the SEC or Big 12, so those matchups may or may not be perfectly aligned, but you'd assume it WAS a battle of the best vs. the best, so there should be some merit to this argument.
Conversely, that makes the SEC's non BCS title game record 29-18, with the majority of those matchups coming in bowl games where the matchups are usually relatively even. It's not as if a 6-6 Kansas team would be lined up against a 10-3 Georgia team as it might happen in the regular season. Yes, the bowl matchups can be a little lopsided (Iowa vs. Oklahoma last year, anyone?) but I think that's about as telling as one can get in terms of overall conference strength.
That being said, it's not as if A&M and Missouri have done much more than occasionally get in the rear view mirror of Oklahoma and Texas the past few years. Once you get past those two teams in the Big 12 the next best competition is going to be Oklahoma State, Kansas State or Nebraska (previously) who will occasionally make a run at a conference title, but are usually respectable 8-4 or 7-5 teams. Compare that to the SEC West, where third place Arkansas last year was ranked third in the country at one point (behind the first and second place teams) not surprisingly. Yes, A&M had Arkansas on the ropes, but that was at home and the fact of the matter is that they lost. No Tannehill this year will make things even tougher...
Not sure what everyone else thinks about these teams, but I anticipate no more than three wins for either this year in league play.
Here's some interesting numbers on the SEC and Big 12 as far as the winningest teams: