From Shooting Illustrated: https://www.shootingillustrated.com/articles/2017/3/24/did-the-single-stack-nine-kill-the-carry-revolver/
by Kevin Creighton
Friday, March 24, 2017
Once upon a time, police officers who patrolled our streets carried revolvers on their hips. Guns like the Colt Police Positive and the Smith & Wesson Model 19 were their primary defensive firearm, and they carried .38 Spl. snub-nosed carry revolvers like the Detective Special and J-Frames for backup guns and when they were off duty.
They carried those small revolvers because they were small, easy to conceal and had a manual of arms that was more or less the same as the guns they carried for a living. The snub-nosed carry revolver also had the advantage of using essentially the same type of ammunition as their service revolvers, so the transition from full-sized service revolver to compact concealed-carry gun meant dealing with more recoil and less accuracy from the smaller gun, and that was about it.
Today, though, police officers are far more likely to carry a Glock or a SIG Sauer or a Smith & Wesson M&P semiautomatic pistol than they are a .38 Spl. or .357 Mag. revolver, and guns like the Smith & Wesson Shield, Ruger LC9s and the Glock G43 are reflecting that new reality. Smaller, lighter and easier to conceal than their full-sized cousins, small single-stack 9 mms are becoming a popular option for people who want to carry a pistol with them, but find that carrying a larger gun like a Glock G19 or SIG P320 is just too much to deal with on a day in, day out basis. I myself prefer carry a larger pistol whenever I can, but there are some times when the occasion demands more discretion than firepower, and that’s where the thinness and light weight of a single-stack 9 mm really comes through.
A miniature 9 mm also offers you the advantages of the same manual of arms your larger gun. If you’re used to a striker-fired gun, the operation of the Ruger LC9s or Glock G43 will seem like second nature to you, just like the operation of snub-nosed revolvers mimic the operation of their larger cousins. My fingers goes naturally to the magazine release on my 9 mm Smith & Wesson Shield because that’s where it is on the large semi-automatic pistols that I occasionally carry, and the methods I use to clear malfunctions are pretty much the same between those guns as well.
The reasons to carry a subcompact, single-stack 9 mm over a larger pistol are also essentially the same as reasons to carry a small revolver instead of full-sized gun. With the right holster and appropriate cover garment, it’s fairly easy to discretely carry a full-size 9 mm on a daily basis and without tipping people off that you’re carrying a pistol with you. However, it’s even easier to conceal a smaller gun, and a smaller gun also opens other options like pocket carry that are even more discreet.