"Pistol calibers are pointless, you should get a short rifle for CQB" seems to be a prevailing comment from the last decade since massive interest in the 10.5 in Mk18 style AR15 rifles became popular on the internet...

... but how many of these people have actually shot tiny rifles in confined spaces? Since PDWs are most likely employed in tight, cramped locations (indoors, hallways and vehicles), we think concussion absolutely should be a consideration before one decides that the short rifle caliber PDW is the solution to your requirements.