Usually I will give the edge to hitters, but yes Milledge has big plate discipline issues and though he has big potential ... I'm not sold that he will defiantly make it.
On a mix of potential and own personal opinion I'd rank them like...
Butler - given a full year, could move higher. better hitter then Milledge and should move faster
Morales - don't have a good enough read on him to put him higher