Go check out the rankings, which include detailed comments. Schaum spends a ton of time on the minors and is one of the best sources, maybe the best, on this topic.
Random rankings of interest:
- Mike Montgomery tops the list.
- Wil Myers is ranked 3rd.
- Chris Dwyer is ranked 6th.
- John Lamb is ranked 9th.
- Eric Basurto (Gload trade!) is 28th.