Since it's his hair, he gets to decide what he wants to do with it. I wouldn't want him telling me how to style or cut my hair, so the only fair thing to do is to let him decide this question for himself.
Ladies, what would you do if your boyfriend had longer & prettier hair than you? Curl it, have him cut it, etc?
Leave him alone.
I always had a rule that I didn't date a guy who had longer or prettier hair than I. If it bothers you find someone else. Or ask him for tips on how to get that pretty hair. ;)
I'd wrap my fingers in it!
Comb it, cut it and style it for him.