I'd go with Wagner. He lead the team in points per minute last year. He'll be better at staying on the court. They won't have someone more versatile (like DJ was this year). And he'll have some huge games that will prop up the scoring average.
Simmons and Matthews are wild cards, but I'm not sure either will be huge volume scorers at Michigan. It won't be MAAR (won't get substantially higher usage) or Robinson (defense will keep him from getting enough minutes).