In comparison to long guns (rifles and shotguns), pistols are smaller, lighter, and easier to take. Since firearms don’t rely completely on the user’s potency, they get poorer people on an equal basis; when Colt produced the first functional repeating pistol, it gave rise to the saying “God created men, but Colt made them equal.”
Since using a pistol, at the very least, needs one hand whereas long guns frequently need both, that leaves a free hand to a pistol user. One example of where this is an edge is with tactical lights, where the light and pistol may be utilized alone or in coordination; mounted lights, as used on long guns and submachine guns, do not let the light to be leveled independently of the firearm. Additionally, pistols can be readily used and for that reason the user can simply change firing hands determined by the specific situation.
Another significant tactical concern is maneuverability. In close quarters, an adversary could more readily wrestle a long gun’s muzzle to a posture where it’s not covering him, or could more readily wrestle the gun away from its owner, whereas a pistol offers little to catch, and also would be much more likely to still be covering some part of the competition during the battle.