As a resident Leach fan, I just want to say I agree fully that his ceiling is likely south of National Championship football. I believe, as I've stated, that he will turn games into a track-meet, where he'll likely lose some he shouldn't and shock the world in others. He's hard to prepare for.
On the other hand...nobody we have hired since Phillip Fulmer has coached championship winning football. Natty's are hard to come by...look how many traditional programs have never won one, and how few see it within reach on a yearly basis. The goal should be first and foremost winning the East. That is winning football and gets you in the position for bigger things. Beating your rivals, and winning your division is step one. That is the kind of football I think Leach can achieve on occasion, though in the West it may be more difficult.
Pruitt has, I think, more potential as a sustained long-term success...and probably more likelihood to be a National Championship caliber coach, though that is distant right now. But don't believe for a minute that Leach wouldn't have been a vast improvement over what we have experienced since CPF, and could have made things very interesting with Florida, Georgia, and Bama. I'm certainly glad he's in the league to give Saban something else to concern himself with.