This really depends on what kind of player you'd want on your team. I admire both McCoy and Morris but for different reasons. McCoy, though, would probably give me more sleepless nights if I was a defensive coordinator simply because he's just so darn good as a pass catcher in addition to his talents out of the backfield. Morris, on the other hand, is very physical and, though we haven't seen a lot of him, I think he's going to prove to be equally durable and productive, read option or not.
As for Murray, I still believe in him. It's hard to ignore his production at Oklahoma. The guy did everything and did so with nagging injuries throughout his final year. I think he's just been somewhat unlucky as a professional having suffered injuries that have kept him out of the lineup, but if he can stay healthy for an entire season, and if the offensive line can improve even a little in run blocking, I think he's going to change people's opinions about him. I think he can be just as productive as the other two given the chance.