I'm not sure about either of them. I worry about Robin's back and Earl's head. Robin clearly has the potential to be the starting center we've all dreamed about here but you just never know with back injuries.
Clark is a different story. I'll go into next season hoping to see the same kind of improvement from him that we just witnessed from Goran and Lopez but I have real doubts. No one has ever questioned Earl's potential but there have been a lot of issues raised about his head/heart. If he ever puts it all together he'll be a huge plus for this team but there is reason for concern.
Steve
I'm not sure Clark's play was necessarily attributed to his "head/dedication" as it was his on-court experience/mechanics/nerves his rookie year. From the games I saw where Earl played, he looked really jittery and lacked self-control (as if he drank twenty red bulls and was going 150mph on the court). I really think if he slowed the game down and let it come to him, we could see a completely different player. The kid already has a pretty good jump shot and ball handling skills especially for a 6"10 big so he has the potential to develop. Offensively, I don't know if it's on par with Amare, but his Defense (from his limited minutes) is light years ahead.
In terms of the unknown/underdevelopment of Clark, we could have said the same thing about Dragic and RoLo last year. In fact, that seemed like the general consensus on the board...