If you want a cartridge that will penetrate the heavier ballistic vests either a .223/5.56 or a 5.7x28 will do that and of course so will various larger calibers.
A 14.5 inch AR-15 w/ pinned muzzle device would be my choice for a self defense rifle that will penetrate ballistic vests since they are not expensive and there are lots of choices. Or an SBR if you want to go through that process and spend the extra money. I shoot a lot of matches with a PCC (a JP GMR-15) and like them a lot, but a PCC wouldn't be my first choice for a home defense gun.
I had one of the older Ruger PC-9's and it was reliable, but I prefer the AR-9's.
