9mm is perfectly adequate these days. Bullet technology has 9mm hollow points expanding to some very respectable sizes, and they're much easier to control than larger caliber handguns, and shot placement is paramount. I agree that rifles are far superior to handguns but then again the best equipment is the tool that you can carry the easiest and most often. If shyt hits the fan, walking around with a drummed AR is just asking to get yourself shot by an unassuming person with a concealed pistol.
This thread should actually be called, "every person should own a shotgun" to be quite honest
Here's my rifle collection just for shyt's and giggles. I got scopes with quick detach mounts for the two on the bottom to give out that long range work if the situation calls for it. The red dots are for quick and dirty hoo rides though.
Edit: Just watched the OP's video. Run a bunch of rounds through that drum before trusting your life with it. 100 rds ain't shyt if it jams on the third shot.