Here is the thing. I think there is a chance Mac has a better NFL career than Tua, and I am not factoring in the chance for injuries. I am saying this under the assumption they both remain healthy.
Mac isn't going to be drafted as high as Tua was. He may not even go in the 1st round, though I think he will. But the way he plays the game translates into a better chance at a long term NFL career than Tua. I think Tua's athletic ceiling is higher than Mac's, yes. But only if he can learn how to stay healthy (and much of that is player driven, not just simple good luck/bad luck). And his first season with Miami just does not look good, but I really believe a lot of that is the surrounding cast and Chan Gailey. They clearly called a different game with Tua in vs. Fitzpatrick. But some of that is on Tua as well.
I hope both guys turn into NFL All-Pros. How awesome would it be for Alabama fans? But if you are asking me which QB I want to run my team... I think I'd pick Mac. It's really close. Really, really close.