Ruger supports gun control.

Cost: filling a G17 mag is a little cheaper than filling a G21 (currently).

More rounds: a G17 mag has 17, a G21 has 13.

I like to pick a round and then use it across the board. Total cost of ownership is mostly ammo not the firearms. So if you are already in a bunch of 9mm and have little-to-no .45, it probably makes sense to stick with 9mm. If you are already in a bunch of .45 and have little-to-no 9mm, it probably makes sense to stick with .45. Along these lines you might want to get rid of the .380 because it's similar to 9mm but is almost as expensive as .45.

Pistols and/or shotguns are probably fine for home defense. I don't know how one can avoid hearing loss in a home defense situation.