Tough question.
I chose Matthews because I think he has the best chance to be drafted by a team that will put him in the best position to succeed. Say... the Patriots or the Parcells run Dolphins. I think Clay has the intelligence, work ethic and heart to never quit. To always try and be better and that's what sets him apart, IMO.
Maualuga was a close second for me, strictly for the fact I think if he gets selected by a 3-4 to play in the middle. A team like the Chargers or Broncos in the middle of the first. I think that's the best opportunity for him to succeed and if he goes to another team where he doesn't fit, will be a bust.
I think Cushing could have a solid career in the NFL but I don't think he has the potential like the others have if they're all put in the right scheme.