"*Most kinds of .45 have unexceptional muzzle energy and are big and fat, giving fairly poor performance even against light, flexible body armour. It was the standard US military pistol round for a long time and many diehards still swear by it, but people who carry guns for a living - cops, soldiers, criminals - are mostly using other calibres these days. (Some spec-ops troops still use .45, as the bullet is subsonic and thus can be effectively silenced.)"
For the record, this is pure unadulterated bullshit. The .45 was invented by John Browning in 1911, several years AFTER the 9mm was invented. It was designed with the intent to be the ultimate man-stopping pistol caliber. Its velocity is slower than the 9mm, but it has greater foot-pounds of energy due to its much higher mass. Its wider shape also gives it a more devastating wound channel. FBI statistics rate one-shot-stop capability of the 9mm at about 92%, and the .45 at about 96%, if I remember correctly.
Throughout the 1980s and early '90's when law enforcement was transitioning from revolvers to semi-autos, the 9mm was the most ubiquitous. In more recent years, many agencies are going to the larger calibers of .40, .45 and other more modern calibers such as the 357SIG.
.45 is very popular among conservatives though, but not a whole lot more than any other caliber. .380 is one of the most difficult to find now due to the spike in popularity of tiny concealable autos.
So yeah, BULLSHIT. But the ammo shortage is real, just go to any Gander Mountain or Cabelas and you'll see.
Edit: Oh, and subsonic?? You ever hear a .45 go off? Read the muzzle velocity on the side of a box of .45, do the math, and tell me whether you still think that's subsonic. The highest caliber that can be subsonic that will fire reliably is the .22. The author didn't even do the most basic of any research.