Rifle Shooter has a piece up comparing and contrasting pistol caliber carbines.
James Tarr compares the Colt AR6951, Rock River Arms LAR-9, Lone Wolf Distributors G-9 and JR Carbine. He finds pros and cons with each, but to me Colt is dead until they move to a free state. The JR Carbine had forend components come loose under recoil. Of course, this is fatal in my opinion.
I would select the RRA carbine for lack of any other test, but that’s probably because I have a RRA 5.56 mm rifle and like it. I have two carbines (5.56 mm AR-15 and M1 Carbine), but no pistol caliber carbine. I have shot a Colt fully automatic carbine.
At the present I’m not convinced enough in the utility of a pistol caliber carbine to spend a great deal of money on one. I can see the utility of a SBR in pistol caliber in the AR platform so that one could attach a tactical light and reflex sight for close quarters home defense, but this can also be accomplished with hand guns. My have polymer frame semi-automatics and perhaps the best CQB weapon ever invented by mankind, a S&W .357 magnum revolver.
Why do I need a pistol caliber carbine? Perhaps for my wife to shoot to avoid any recoil? What would other aspects of utility be for the pistol caliber carbine? Readers can weigh in on this question.
UPDATE: I should have added that I do not and will not have a SBR because I will never register a firearm with the ATF.