I haven't used either very often, and don't think I've ever used Bosman, but looking at some normalized numbers, which of these pitchers would you prefer:
A: 174 ERC+, 165 HR/9+, 112 OAV+
B: 176 ERC+, 171 HR/9+, 108 OAV+
Pretty close, right? But pitcher B has 80 more IP. That's Peterson, so that's who I'd take if I were looking for a starter in a 4-man rotation. But for a five-man rotation, either would be fine.