More than stopping power counts
I think to much emphasis is placed on velocity, caliber or bullet weight.
RECOIL should also be taken into account. My home defense guns are usually 9m.m. because recoil, even with +P loads is moderate. For me, the combination of large magazine capacity, reasonable recoil and grip size are the deciding factors.
My wife uses a 9m.m. SIG 225 because it is just large enough to get a good grip on with reasonable recoil using COR BON Powerball ammo, but not so heavy, that it is hard for her to hold.
My duty gun is a .40S&W, but it is not my choice, even though the recoil is not that bad.
I tried the really small guns and came away unimpressed. Off duty I usually carry a SIG 232 in .380ACP or .32ACP BERETTA Tomcat. In the summer, they are much easier to conceal than a BERETTA 92Compact or WALTHER P-99.
Even my SPRINGFIELD ARMORY XD9 Sub Compact is hard to conceal in a Florida summer.
On the other hand, I had a KAHR 9CW and sold it as the recoil was to severe. Same for a first generation COLT Cobra. The COLT was actually painful, even with wadcutters.
I recently shot a .32ACP NAA Guardian and it was work because of the recoil. Remember, this is from a .32ACP!
Recoil can have an effect on your accuracy and the recovery time between shots, so I will always choose the round that gives me the best balance of control and power.
For different individuals, this will vary a lot. More in fact that the stopping power argument.
Jim