Killing is easy, stopping is another matter. What the '86 Miami Dade shootout proved, that eventually led to law enforcement's wide spread adoption of the .40S&W. Bad guy got shot full of 9mm but continued on to kill officers before realizing he was already dead.
The bad guys (Platt and Matix) were (IIRC) wearing bullet resistant vests and armed with rifles. The FBI agents (many of whom were armed with 38 Special revolvers - FBI was transitioning to 9mm autos at the time and let older agents retain their familiar revolvers) were under-gunned and vulnerable.
As a result of the Miami disaster, the FBI studied improved firearms and ammo (adopted the 10mm Auto, then the 40 S&W, but found the recoil an impediment). Eventually, they developed new loads and better bullets for the 9mm and adopted them. According to some sources, these new loads are as effective to the 45ACP.
