I disagree a bit... Although, it is always a crap-shoot to rank over 100 QB's succinctly.
The system is predicated on making the right throws effectively and efficiently. Now, it's trained and beat into the player through 1,000's of repetitions, but the throws he's making are all the routes and combos that he'll throw at any level.
He's trained to make the correct decision by one or two read keys. It's basically what every team in the country is doing to some extent.
Now, does he have top-5 arm talent in the country? Probably not. It's fine to get the job done by a large margin though.
Decision making, I think the difference between most of these guys countrywide is negligible, it's all what you're taught to some degree. I mean I'm far from sold that any QB being talked about at the top of this draft has superior decision making ability.