Which .45 ACP load in my Sig Sauer P220 is better for personal defense - 230 grain or 185 grain?

The difference between the two is small enough that I wouldn't focus as much on the more powerful one. Shoot some groups with both to get a feel for them. Do you like the recoil of one vs. the other? Check the groups. Chances are the one you are more comfortable firing will get better groupings. Go with the ammo that groups better for you and your Sig.