This is just so personal.
I'd go for expansion over penetration.
I CC 9mms and 45s. More than likely, at night, bad place, I'd have the 45.
That weight thing, IMO forget it. If CC means so little to you that you're
willing to restrict the weight that much, maybe you should be carrying a light, or
a knife or something. I'd be much more worried about making the carry
comfortable, as oppose to an exact weight paradigm.