So much lol on this thread. The youtube guy spent one "tour" (three weeks) as a contractor guarding a latrine. Completely devoid of any skill or knowledge. Has never discharged his weapon on duty as a cop and was fired after a short time on the job. He has never served in the military.
AR's are a shit home defense weapon. Over-penetration is a huge concern inside a home, unless you live in a concrete bunker. Frangible bullets--but then you're better off with a .45. A Glock 21 or preferably a HK45 or HK45C. A carbine in a pistol cartridge is ideal, but that Hi-Point is not known for reliability.
A rail-mounted flashlight so that you can distinguish between friend or foe. Lasers are retarded. Minimal utility as a deterrent--and would you want to be in a situation in which you're praying that the intruder will be scared-off if you put a dot on his chest? lol to head-shots. You are summarily f*cked if the guy has is motivated and wearing III-A body armor. You're trying not to piss yourself as the dot is wavering three feet off-target.
ARs are defined by their operating system; either DI (direct-impingement) or piston. The M16/M4 are DI guns. The gas acts directly on the BCG, thereby cycling the weapon. In a piston gun the gas acts upon an op-rod which impacts the BCG to cycle the weapon. The piston gun can be run dry (minimal lube on BCG). The DI guns should be run wet due to fouling inside the receiver from the gas tube.
The Steyr AUG is a piston gun (NOT an AR) with an OAL of 28". Much shorter than any AR, including any of the carbine-variants. It's a very clean running weapon and is considered state of the art. The bolt rides on two rods within the receiver. Steyr ran >16K rounds through the gun in a few hours time.
Go with a piston AR if you must have an AR-platform. PWS, LWRC, HK, etc. The HK MR556 is the best of the piston guns. There is another piston maker that I cannot recall at the moment. They are a govt-contractor who makes ARs for the civilian market as well. KAC for a DI gun. Tsing Tao has a FN SCAR Heavy in 7.62, but they lake a "light" version in 5.56 as well (.223). Excellent weapon. A good AR piston gun runs from $1500-$3000. The KAC DI is $2500. The AUG as outfitted is around $3000.
AR with self-defense loads (Corbon) or preferably frangibles. I have two AUGs inside the home and two .45 pistols. One of the AUGs has a 9mm conversion and it is my go-to home defense weapon. The other AUG mags are loaded with Ballisticlean .223. A Surefire X300 Ultra rail-light and a Trijicon SRS RDS set on the lowest (visible) output. Keep the house dark and both eyes open when practicing with snap-caps inside the home.