I never really rated any of these two, but this season I've been impressed by Duhon and his ability to do all the little things in a game. He may not be an amazing player, but he's solid on defense, plays hard all night, and doesn't shy away from taking big shots. Of course, this has no relevance in the main topic at hand, but it's still my reasoning towards voting for Chris.
Oh, and, Jamal Crawford would never have been able to somewhat "put the breaks" on Iverson like Duhon did on Saturday. Even the ref got on AI about it.
Jamal Crawford strikes me as a bit more rangy a defender, able to deny and contest shots a bit better with his length, but Duhon seems to be the better overall defender and used to playing pressure defense.