Boy: He's unwilling to look honestly at his issues. All of his problems are external -- caused by other people, shitty circumstances, bad luck. He's not yet taking full ownership for the things that happen to him in his life.
Man: He is man enough to know what he needs to work on and takes action (without coercion) to become a better person. He can admit his faults even if it means swallowing a Big Gulp's worth of pride. This means that he's looking at you, too. He's going to call you out on your BS and expect you to be just as willing to change. Touche.