I have to apologize - I'm having some fun and making light of this thread, just a wee little bit.If things have gone so far downhill that I have to worry about getting hit multiple times with a .308 or get sniped with a .338, I'm going to be concealed carrying an AR pistol. That's when it makes sense to carry 45+ rounds of ammunition on you. But at that point, the only reason I'd be leaving my home is to get supplies.
http://lonelymachines.org/mall-ninjas/
I like the academic exercise, but the reality is that although the 10 mm is definitely a much more powerful round, if you do your part behind the gun and put rounds where they are supposed to go, it's likely not going to matter what you are shooting as long as it's not under-powered or too small.