Tim Tebow is a gimmick QB in a gimmick offense. (His most notable predecessor under Meyer is Alex Smith.) Why is Tebow returning to Florida next season? Maybe it's because of his slow, slow, slow release and his inability to properly read defenses. Maybe it's because he'd be a second round pick this year, and wants to improve his status. Maybe it's because he knows he'll get clobbered by NFL defenses, and injured severely, if he doesn't improve his overall game.
Vince Young, on the other hand, is a stud. He's mobile, he has a quick release, and he's hugely clutch. His biggest weakness has been his mental anguish this year over God-knows-what. (I would gladly trade places with him.) But since leaving college, he's been drafted in the first round, gone to the Pro Bowl, led his team to the playoffs, and won the offensive rookie of the year. He'll be back next season.
I'm fairly confident that, five years from now, Vince Young will have a Super Bowl ring, a Super Bowl MVP, and several Pro Bowl appearances. Tim Tebow will be riding the pine for the Eagles, or something.