It would be better to break down the categories into Mil-Spec-ish, Gucci, Race Guns for action shooting, PDW/HD mini-ARs, and Hunting rifles.
There are a bunch of companies that have entered the market over the past 10 years doing some interesting things, and a lot of others who are chasing the lowest price points that miss the mark in quality, reliability, accuracy, and TDP compliance.
I. Gucci ones that interest me are:
Cobalt Kinetics
GAP
MSTN
That company with the EDM-cut receivers and taper-fit barrel nut, forgot the name.
LaRue
LWRCi
Nemo/2A
Noveske
Precision Firearms
SLR Rifleworks
II. Race Guns default answer is JP Enterprises, who pioneered the AR-15 race gun. Cobalt Kinetics had some crazy race guns before the new ownership stopped all that.
III. Mil-Spec type blasters with basic forged receiver sets and tight tri-bore carriers, quality bolts, chrome-lined barrels, correct gas ports, springs, small parts, great build quality is KAC, FN, BCM, and DD. KAC takes reliability and other details in their own direction with little improvements with the bolts, gas system, receiver features, muzzle devices, suppressor use optimization, and ergonomics. I see some good things from some of the new entrants in this space, but don’t have any hands-on with them (SOLGW, TRIARC). Should add Centurion to the list too.
BCM
Centurion
DD
FN
KAC
SOLGW
TRIARC
IV. PDW/Mini ARs are still being fleshed-out, with different ideas and departures from the plain Jane AR world:
Q
LMT
Maxim Defense
Noveske
SLR
V. Hunting Rifles
Alexander Arms 6.5 Grendel
JP 6.5 Grendel
LaRue 6.5 Grendel
Nemo/2A Armament 6.5 Grendel / 6mm ARC/ 7.62x39
Wilson Combat 300 HAMR / 6.5 Grendel
There are a bunch I’m overlooking for sure. I didn’t know 2A Armament got bought-out by Nemo.
If someone is looking for Mil-Std carbine blaster, easy answer is BCM. If they are bored with the Mil-Spec looking guns, venture into any of the Gucci, PDW, Hunting, and Race guns if they want. I’m at the end of my 4th decade of shooting, building, accurizing, and messing with AR-15s, so I’ve seen a lot of different changes and unexpected evolutions over the years. My perspective is a lot different than 10-40 years ago. I’m currently into the 6.5 Grendel PDWs.