Quinn's drop was a shocker to pretty much everybody I think. They DID show footage as to why, and it's apparent that he's got some problems with technique. However, that can probably be fixed with the help of a good QB coach. The kid wants to play (and in Cleveland) more than anything in the world.
There's no doubt however that Russell is the "natural thrower" while Brady's not--but sometimes heart can overcome lack of natural ability.