20+ years in law enforcement. Hundreds of autopsies attended, and have seen guys who took .45 ACP and 12 gauge slug and still fought back, both physically and with a firearm.
Stopping power is shot placement, period.
The .40 S&W is nothing more than a way for S&W to make some money out of the 10mm after the FBI walked away from it.
The .357 Sig is a copyright ripoff of the .38/.40 Clarke.
Too often, people buy certain calibers/guns hoping it will make them a better shooter.
The 'user friendly' .40 caliber offerings are pretty dismal in performance.
Just look at the November 2006 Geroge T. Deeb shooting for evidence of this...FWIW