On this team you should always go with the higher OBP in my opinion. These guys can score runs if you just get on base.
Pena also has speed, though not as much as Crisp.
EDIT: both OBPs are pretty pisspoor. We're trying to choose between a .314 and a .327, one a middle of the order guy (yuck) and one a top of the order guy (yuck). The fact that their SLGs are similar is odd, given Pena's supposed power.