As time goes on, I believe more and more that until you get above common defensive caliber handguns, caliber is a ways down the list of importance when it comes to 1 shot stops. Most handguns just aren't that effective. I assume the primary factor in most 1 shot stops is fear. "Stuff" gets real when bullets start tearing through you. After that, I would assume are pain and, of course, shot placement. Obviously, a cns hit should result in an immediate stop.
"Those who would give up essential liberty to purchase a little temporary safety, deserve neither liberty nor safety."
- Benjamin Franklin