Some do with Wolf. Good pointsI don't think there is a "Best Choice". It depends on the person carrying the platform. Can you carry it? Can you operate it? The secret is, like you've alluded to, is to practice with your choice.
If I have to bugout, I choose all of my weapons, since I bought each of them with a purpose. That implies I have the ability to transport them. If I could only have one, I would choose my AR15. The ammo is plentiful, cheap and fairly light, and can still stop a threat.
As far as the question of steel case ammo, that will depend on the make of the weapon and the ammo manufacturer. My AR gags on Wolf ammo, so I avoid it. Other steel cases worked fine, but now ammo is so cheap, I stick with brass.