The Cartridge is very carry gun dependent for me.
G-26 is my most powerful comfortable to carry conceal gun
hence my fav is 9x19. Pocket Carry works. Iwb works.
Model 36 snubby is next so .38spl. Pocket carry works.
SP101 .357 mag in an IWB a little too big for the pocket.
Favorite to shoot at the range is .45 ACP bu the lightest gun I have is an officers ACP, IWB only no pocket carry.
New gun is Keltec p32 pocket carry is easy, and this is my deep cover gun.
I expect that if I have to use a gun for self defense it will be at arms length distance, so .32 acp in the head or eyeball will be effective.
Practice drawing shooting and carrying are more important than the caliber. Element of surprise and accuracy at 5-10 feet is key.