I also think Green's biggest weakness his first two years is that he ended up being a poor shooter who was really scared to miss from deep, which is a thing that I think will also effect Black at first (for how long I do not know).
I just see a lot of chances for Black having a similar role to Green to start his career, especially if he goes to a team with established lead playmakers. Josh Green's passing went overlooked at Arizona, but he's a great passer. He showed a lot of upside this past season with some huge games as a playmaker and his shooting has come along (though he hasnt gotten to where he is doing it with volume).