Don’t own one. My feeling is that they are probably fun to shoot. If, however, you need to put a wrist brace on it to make more effective than just fun, you might as well buy a carbine.
Novelty item. They are a thing because people don't want to (or can't) jump through the hoops to get a legal SBR. An AR "pistol" would be a joke, if this was a rational world.
5.56 pistols? Range toys. Far too much power thrown away to make noise and fire.
this discussion would be greatly improved by not conflating barrel length with receiver's designation of pistol or rifle or "firearm"
there is a world of difference between AR15s with like 7" barrels and no brace that are typically low quality range toys, and ARs with 10"+ barrels that are designated as "pistols" for legal purposes to
- allow carry in some states where you can carry pistols but not rifles
- to avoid the hassles that come with SBR, including getting ATF permission every time you cross the state line
keep in mind the standard issue M4 that the Army uses is a 14" barrel, and there are a ton of 10.5" barreled ARs used by the military. So barrels under 16" doesn't immediately make them "range toys".
556/223 in a 10-14" barrel will still achieve enough velocity for m193 to reliably fragment out past 100 yards.
After reading your responses and doing some additional research, I think I'm sold on the CMMG Banshee 300 and not the SBR. I live in Kansas and can carry it in the seat beside me. Heck with my CC license, I can even get a mega shoulder holster and carry it. My chief interest is home/self defense and some range fun when ammo prices become more reasonable again. I really don't think the SBR carbines will work for me. I already have a custom AR 15 .223 that is a kick-ass rifle. Only way I would have one is if it was suppressed. I've already lost enough hearing!
I'm not a huge fan of 9mm ARs. I prefer platforms that were designed around blowback operation and the handgun calibers like CZ Scorpion or B&T. That's not to say CMMG's delayed blowback system isn't ingeniously shoe-horned in, but it's still a shoe-horn job.
I also have 300BO ARs and bolt guns. It's a great caliber, especially for pistols with barrels under 10". I prefer 223's ballistics in barrels over 10".
I have both SBR and pistols, and they both work great. I keep both mostly in case the legal environment changes.
for your home, i'd stick with your custom AR. For vehicle carry, a 300blk with 8" barrel or 223 with 10.5" barrel "pistol" with brace is a great choice
the advantage to 9mm carbines is they're phenomenally easy to point and shoot, especially suppressed. very very easy for new shooters and people who never practice to get some hits. That's not particularly true for ARs in 223 or 300blk. Using a 9mm carbine for HD or vehicle carry is also a great choice, but understand there is still a huge difference in terminal ballistics between a rifle and pistol caliber (i.e. % of hits goes up with 9mm, but those hits are less effective. maybe they're effective enough, but still less than a rifle caliber. And hits are way more effective than misses.)