For the purposes that you described I would prefer a 4" over the 6", however, you already own one so that is really up in the air.
Forget the porting, another downside of porting is that if you used the gun in a darkened room (home defense or outside at night) the bright white-orange flash shooting up from the ports could cause you to be momentarily blinded (loss of night vision) and unable to see for follow-up shots.
Rather than porting I would by a low recoil self defense load as sold by Federal and many other ammo manufactures.
VH