As a guy with a well documented disdain for the AR platform in general, I can say what it is for me; the flexibility.
But . . .
1) I don't shoot run of the mill FMJ. Ever. I can't afford that and the performance is substandard.
2) With the same gun I can shoot 230gr bullets that hit like a ton of bricks so quietly you really don't need ears on even unsuppressed, to "AK-47 +P +accuracy".
But . . . admittedly the mechanical issues of the AR platform still exist.
Jafar kinda talked me into giving the AK platform a try - I know this is a coming out of the closet for me - but I like it. It is NOT as flexible, but undeniably it is a solid, reliable, combat effective weapon, one I could afford to feed factory ammo. I used to poo-poo all MBRs that didn't start with an M1 . . . but even closed minded 'ol SOBs like me can learn new stuff.