In my opinion:
Pocket guns - to protect you from muggers
Ankle/shoulder holsters - to protect you in an active shooter situation.
In a mugging situation, a .380 you can draw from your pocket in 1 second is better than a 10mm that takes you 5 seconds to draw. Advantage pocket gun.
In an active shooter situation, chances are you will have more time to react. In that situation, carrying a bigger gun in a ankle/shoulder/IWB holster makes alot of sense. If I'm going somewhere more risky, I find somewhere to carry my Beretta 96. I can't draw it quickly, but in a situation where I'd need it I should have time to get it.