I use this guide when buying a caliber I have not owned before, or know very little about. The guys who wrote this have published work to their names. Does that mean they are experts? Who knows? However, they do know more than me.
This is a guide to help you select the best ammunition for your defensive firearm. Most of these opinions are based upon the work of Massad Ayoob, Evan Marshall and Ed Sanow, police officers who have extensively studied the issue of firearms, ammunition and stopping power. I refer all interested parties to the excellent series by Ayoob (In the Gravest Extreme, Stressfire, The Semi-Automatic Pistol in Police Service and Self-Defense, Stressfire II: Advanced Combat Shotgun) and the comprehensive book Stopping Power by Marshall and Sanow.