McCarron can stay with Ms. Alabama - he's a good QB on a great team, Bridgewater is solid but no Clowney level of dominance & Manziel is a great college QB, but due to his playing style, height & suspect arm, I'd venture to say he'll be a slighlty better version of Colt McCoy & lesser version of Drew Brees.
Your logic is like not taking Bruce Smith in 1985. You take the players who have HOF potential that were dominant in college.