Do you understand that they sell guns that aren’t 9mm. Also at that range training is all what matters. All pistols (except some revolvers) are semi automatic, it’s nice to have a stock and a bit more stopping power but a pistol can %100 combat a rifle this isn’t call of duty. Also people chose 9mm to get more rounds in the magazine, putting 17 shots of 9mm is better than 11 of your super armor penetrating 10mm. Also weight and recoil, plus body armor doesn’t make the bullets disappear it increases your chances of being taken out of action rather than killed. Your ribs will be broken if you get shot with a vest on even by a 22lr even pistols are very lethal.