The idea is to destroy the enemy, or the enemy's will to fight, if I recall the quote. A solidly placed round will do the latter. Kill a man, that's one man out of the fight. Wound a man, that's two men out of the fight if someone stops to help him.
I carry a FiveSeven these days. Used to carry a Sig .40 cal because it was required on duty, and I didn't want my reactions marred by carrying different firearms. I prefer the FiveSeven.
Sorry - I know this is a S&W forum. I've carried 686s, Chief Specials, 4609, as well. Also m1911.
In the field, I plan to carry the 460V: round selection chosen by enviroment.