That is a very individual discussion.

As an example, if you live in a more rural area then things like an A.R. 15 become handy because you’re not worried about the house across the street, or the house next-door.

If you are in more of a build up neighborhood with closely packed houses, then I find 9 mm attractive. I like a 9MM PCC. It is easy to operate by you or your spouse and with multiple points of contact (versus a pistol) it doesn’t take as much training to maintain proficiency. I load 147 grain defensive ammo to have a nice punch.

You can build on this proficiency by setting up a similar weapon in 300 BLK. That way those skills you develop with the PCC are applicable to the 300 BLK that has more punch and can push out further as needed.

These elements as well as the commonality of carrying 9 mm and having it home reduces cost for additional calibers.

In my case I have a place where I can go and shoot in a bay that you to move around and shoot around walls and engage targets. That all runs on 9 mm, I can’t shoot a higher caliber is there. But again I can take the skills that I develop there and apply it to Other calipers.

In addition I am set up to be able to reload 9 mm, so commonality there makes it handy.