The main difference is Aggie fans (not all of them obviously) have a smug arrogance about that damn Aggie code (or whatever it is) that is sorta like a religious document you set aside when it becomes inconvenient.
Both are delusional to the point of psychosis.
Texas REALLY DOES BELIEVE they're one of the greatest football programs in history, but they come up with that idea based on money.
ATM is sorta like Auburn in being a little brother with a bit of an inferiority complex, but the difference is that AMT was willing to set out on their own and leave the conference.
When both lose, the excuses are legion, which is why I should have trademarked "If Colt hadn't got hurt."
Generalizing, that's a pretty accurate take. Of course, I know good ATM and UT fans. As a matter of fact, a lot of UT fans I know have really been humbled the last few years (I say this realizing they are probably the minority). A few I know are actually in awe of Alabama and our success. One deep pocket UT fan I know LOVES CNS and roots for Bama all the time. Now that might change. As for ATM, I've often said their fans remind me a lot of Auburn fans with a little more class, but with even stranger customs. They are generally good guys, but, as you say, the Aggie code is strong.
Now the irony. Aggie fans really felt good about not having to deal with Texas and now they will. I get the impression from talking to a few they are really nervous. And with all the attitude that comes with Texas, I think they really don't know what they'll be up against to begin with, but in the long run, it'll be the best thing that could happen to their program. The first few times they play ATM that may get their butts handed to them. But I think ATM fans realize Texas will benefit from the SEC and they are nervous about it. They see how the SEC made them better and it'll make Texas better too, in the long run.