For me, it's more about practicing the reload than it is about how many rounds my gun carries. I carry a Kimber SIS Pro. In it, I carry 9 rounds of Federal HST or Ranger T-Series. I almost always carry one reload, sometimes two.
All things considered, I feel better carrying 9 rounds in a 1911 than I do any double stack auto. It's just the platform I have the most control with and that shoot the fastest and most accurately.
As for multiple threats, I learned to start with the first and shoot until they stop, then the second and so on. Instead of 1 or 2 into each one. Hopefully, I'll never have to find out which works better!