in my opinion, guns should be a system. solutions to a problem.
like tools, all mine are dewalt. its nice to have a system. they work with each other.
In my house, the pistols are CZ, the rifles are ARs, and the shotguns are 870s. the rest are toys.
mag interchangability, 22 conversion kit interchangability for the CZs and the ARs, common caliber that is easily stocked for all the guns, manual of arms commonality, and after the dollar collapses, you betcha... parts interchangability.
if the cops take your gun after an incident, sure would be nice to have a backup, that is the same type / mag / caliber.
just my take, your first gun in my house will be a system gun, if you want a SECOND gun, personal preference is your prerogative.
Fox brand pepper spray for my wife if she wont / cant / doesnt think the threat level is high enough to carry in purse. a little canister of that will fit anywhere.
sorry, obviously do it however you like, but thats how we roll.