Back in my day, we didn't worry about 'low recoil' and 'cheap practice ammo' for home defense. You had your grandpappy's old .45 ACP Tommy Gun and you were happy! That big, heavy chunk of steel meant business. Nobody was asking about long-range with a pistol round, you just needed it to work in the parlor. But fine, if you insist on this newfangled PCC business. For the competitions you mentioned, you run 9mm Luger. Why? Because every modern competition shooter is a skinny little fella who cares more about the magazine capacity and the milliseconds between shots than actual thump. 9mm is softer shooting, and the stages are designed around it now..for home defense, I'd grit my teeth and say 10mm Auto, but since you whippersnappers only like the little ones, stick to the 9mm with a good, modern 147-grain jacketed hollow point (JHP). The extra barrel on your carbine makes that 9mm hit faster and expand more reliably than it ever would from your handgun. It's the only one of the 'pistol' calibers that manages to be both cheap for practice and almost respectable for duty.