Monetarily, the SEC has been good to them. Competitively, not so much.
I can see where they would find the Big XII much more attractive than the SWC. They were they only non-Texas school in the SWC. I remember reading the teams schedules in the program at one of the few OU/Texas games I've ever attended in the 1960's. The only time the University of Texas ever left the state of Texas was to play Arkansas every other year. Every other game they played, including bowl games, was in Texas.