I think if they had stayed in the BIG12 they would have won the conference title sooner than in the SEC.
I agree. I don't think this move is necessarily about winning the MNC though. Let's be honest here - we haven't had any real shot at a MNC since the late 90's (and even then it was a longshot). And we probably had a better shot in the Big 12 than the SEC.
I do think the SEC will provide us some benefits that will really help make us a perennial top 25 team - I think that is honestly a more realistic goal for our program. We should be ranked more often than not, and I hope that the increased exposure/revenue/recruiting(possibly) will help bring us there.
Right now, A&M needs to worry about becoming a consistently good program - we haven't been for the last decade. We've been very up and down, with more down than up. We need stability and consistent success - even if that success is a 9-3 or 8-4 season. I think we have a better chance of developing into that sort of team in the SEC.
So in short, I don't think we're more likely to win our conference in the SEC, but I do think we are more likely to become a consistently good team in the SEC. I think best-case scenario is the following: we'll be looking at 2-3 years of 7-5/6-6 teams, followed by 5-8 years of (mostly) 8-4/9-3/10-2 seasons. Then at that point we can worry about winning a MNC.
Right now, though, I'll just settle for being consistently relevant again.