Your right about cheap and available I can't argue that, but my thought was more towards not as loud and less muzzle flash. AK47 power from a 12'' barrel due to the use of pistol powders and a better burn before the bullet exits the barrel.
I don't have either one in a pistol now but the closest I came to one was a 12'' .223 Thompson Center Contender, it was loudest gun at the range and I couldn't see after I shot it in low light LOL. But I see your point.