“For stopping effect, they wanted either the .40 or the .45, for what they called “Spin Around Effect”.”
There is simply no such thing. That’s the myth. In the big picture view a typical 9mm and a 45 are so close that its not even funny. The energy and velocity differ only slightly, and certainly not enough to make the slightest difference in how a shot person responds.
And a 45 doesn’t even come close to the energy needed to spin a human body around.
The only question is accuracy and how many rounds you want on board.
Jim Cirillo told a story about someone shooting a Dik Dik in an African camp for pot meat. Twice with a 45 and the Dik Dik just stood there munching grass. Finally after it was dead they looked and there were two nice 45 hits right where he aimed.
His friend asked how could this be? The answer, “I guess he’s never read Col. Coopers book”.
Many 45 shot people never read the book either.