Right now I have all my code using FreeCAD. Besides the base solid and BOP stuff, I'm only using a few trivial tools from the Draft module.
I like the more simplistic naming of FreeCAD functions, i.e. make**** vs BRepPrimAPI_Make****. I don't imagine that FreeCAD could be adding much overhead if any, so I think I will just stick with FreeCAD. Both are using OCE and it seems that FreeCAD has a faster release cycle. PythonOCC is just now coming up on 0.6 after two years since 0.5. In this respect, FreeCAD 0.13 uses OCE 0.9.0 and PythonOCC 0.5 uses OCCT 6.3, AFAIK.