I have carried 15 round Glocks and 5 round J-Frame revolvers. Today I just bought a 45 Shield because it shoots faster and more accurate than the 9mm they had to rent.
With that said: if somebody handed me a card, like on TV, that said "Your gunfight with 3 BGs will happen this afternoon", I would reach for my Sig P226 TACOPS and three 20 round magazines.