The SEC was the biggest game in town before Saban was at Bama, and would still be forever afterward.
I could see why Texas might be a bigger job than Alabama. With Bama, you own the best job in college football. In Austin you'd own a whole conference.
I would like to see him go to Texas though. If he stays at Bama and dominates college football for 10 more years, that's not as interesting as seeing if he can have the level of success he's had at a third school. (Or fourth I suppose if you cound MSU)
I don't see what's in it for him, though. If he's making $6 million or whatever and Texas offers him $20 million, ok, I can see it. But... what does he gain if the money isn't significant?
Moving to an easier conference would help him bolster his legacy from the perspective that it would be easier to win national championships from Texas, I suppose I could see that.