The benefit of AAU is he's been facing guys that's NBA good almost his whole career, while Exum has not. There Lavine adjustment to the talent level isn't as steep as Exum and his confidence level is likely much higher.
For every Durant who can build confidence and whose body advantage translates to the NBA there are 5 OJ Mayo, whose egos are overinflated and career ceilings really destroyed because they would have needed guidance and needed to fully absorb every little piece they could possibly grasp about basketball.
Take Paul George. He wasn't highly recruited, he wasn't the highlight of his AAU team. So he never got that Brandon Jennings entourage treatment.
Have you ever heard that dude speak? He's a friggin numbnut. He was lucky he got the guidance of Larry Bird and was a late bloomer. If he's exploding in 8th grade, I promise you he's never developing lock down defense and he Starburies his way out of the league over the course of his rookie contract.
And that's the issue I take with glorified pickup basketball. These Eurocamps in Treviso that Exum visited annually over the summer and the U18 worldcups and stuff. He's meeting talent there. A lot of guys will play more successful professional basketball than AAU trainwrecks in Europe for a decade.
And if that's not clear enough:
For every Einstein who is a pioneer and has a unique way of learning, there are 100 other very intelligent students that need the best possible education to become skilled in their respective field of expertise.
You don't need LeBron, Kobe, MJ, Shaq, Magic to win the NBA.
Tim Duncan who is just tall and not AAU lobotomized is enough to build a dynasty. And not surprisingly he's playing with players who in majority are from outside the USA...
But I respect everyone's choice. If you're into watching a 5 min dunk only highlight reel of 16 year olds while getting more and more convinced that that's the next big thing, so be it.