I'm a clay shooter, and I'm still scratching my head about the price of 28 ga. and .410 ammo: They're much more expensive than 12 and 20 ga., yet use less of every component.
I like 9mm, but I don't trust the subcompact guns. If I were to carry 9mm, it would be in a Glock 19 or Beretta 92.
Tom