Good question. Short answer is probably: we're all just guessing.
Better answer? Style of play and confidence. Lemond looks completely and totally timid on the floor and doesn't even look to shoot if the game is within 15 points. Seriously. Like Gaffney at his worst. Whereas Ducharme (playing up to 17u) is missing shots but has a good-looking stroke, makes his FTs, and is still aggressive trying to score the ball even if it isn't going in.
I've seen Williams in multiple games over the course of months now, and haven't seen the borderline 5* people have described yet. He has the pieces to be really good, but at a certain point, you either put it together or don't. I'm not saying he isn't a 4* caliber or high-major player... I'm just saying he has clearly looked overrated is all. He'll be a good defender, and will just need to develop his shot. IMO Floyd has a more clearly defined role and path to playing time.
I expect up and down performances, which has happened with a lot of the other guys we're recruiting at Peach Jam. That's expected when you're playing every day, sometimes twice a day.