From an old guy (75 this month) that's done a mix of the gun games starting with skeet and IMSHA (pistol silhouette) in the '70s through action pistol and 3-gun tactical in the 80s thru the mid 20-teens:
The AR15 and similar is the easiest firearm with which to become proficient with, and more importantly the easiest to maintain proficiently, that ever existed.
How do I know? As I've aged and no longer compete, I still go out and run some of the same pistol and rifle drills from when I competed in the IPSC and 3-gun matches.
My pistol times have gone up by at least 50% (sub 8 seconds to ~ 11 or 12) for a standard El Presidente. And these days I cheat by not doing the 180* turn.
But with the AR or similar gas or piston rifles, be it 5.56/223 or 7.62/308, the times are holding so even it's magical. For home defense, I don't think a properly set up AR15 can be beat. Especially as one's reflexes and eyesight go through the aging process.
And why are black rifles so popular? The initial desire to own one still applies and originated with Billy Bob Clinton's AW ban in 1994.
But I still appreciate my other rifles equally well, if not more so