I think Quinn has a better chance than Russell of having a career as an NFL QB, but that Russell's potential upside is much higher. Quinn will likely be one of these guys who moves around from team to team, sometimes starting and sometimes being a backup, but he'll spend 10+ years in the league doing it. In contrast, Russell has a chance to be one of the best QBs in the league -- but he might be out of football in three years.
I don't think either one of them is worthy of the #1 pick. You should be able to get a perennial Pro Bowler (if not a Hall of Famer) with that pick, and just can't see either one of them being in that class. If I have that pick and I don't need a receiver (i.e., Calvin Johnson), then I trade down.