Hell this is tough to answer. If Michael Bush goes on to have the career Curtis Martin did yea thens its easy take Bush with the 77th pick in the draft. But if he never recovers 100 percent from this injury then you wasted a third round pick.
The one good thing though the Steelers have Willie Parker and Fast Willie proved last year that he is an elite RB. So Bush if drafted by the Steelers wouldn't have to save or carry the Steelers running game. So he could take his time coming back from that injury.
As for Dookie. I don't know some people think this dude is all that and a bag of chips? He is a solid for depth. But would you really want him to carry the load if Willie went down with serious injury? I wouldn't and the guy doesn't run like a typical 250 pound big back.