As of right now, the Big 12 has a crisis of prestige. That's it. This can be overcome, to what extent, we'll just have to wait and see. It could be terminal, but it's been caught early and is highly treatable.
The Pac - 12 has internal bleeding. Two P12 athletic departments are bankrupt and only stay afloat because the academic side of their school is covering the debts the athletic department(s) cannot cover. At one school, those debts are going to grow to $40 million a year.
They have the worst TV deal, they have terrible TV numbers and their core founding schools are in malaise. Multiple programs have NCAA sanctions pending.