Hmmmm...what is the defensive purpose of a firearm? should the weapon be unloaded? Man, don't think about this sh** and follow your instincts. Always shoot for the head, any shot. As far as technical characteristics of particular firearms, that is a specific matter of quite some debate...
I've never had anyone come up to me and have a conversation about caliber or capacity while I've been carrying concealed. At least, I think that means I haven't been 'made'. Of course that is not true, as most of us keep our opinions to ourselves. If any law officer said anything remotely...