I've handled and fired probably a two dozen ARs (civilian) and with the exception of the DD, they all looked, felt and fired about the same. Including the two Bushmasters and one Windham I own personally. Granted I spend most of my time treading water in the middle and bottom end of the market. None of the high-end rifles I fired (outside of the DD) felt any different than the mid tier - bottom tier rifles.
Due to being in the Army for 13 years, I've handled and fired at least a dozen M4s and M16s and could tell the difference (aside from select fire) between those and the civilian ARs in how the parts fit together, and the cohesiveness of the "package" despite their age and wear.
The DD was the first that looked, felt and fired (cycled) better than the M4s or M16s I've been issued. It is a work of art in my book. A work of art that meets or exceeds Military TDP... best of both worlds.
Unfortunately they also cost as much as I paid for my first 3rd gen... soooo priorities... heh.
Totally, they are expensive. But you get what you pay for. Daniel Defense makes some of the best rifles in the world. Marty Daniels is a cool guy and set out to be #1. he's killing it. They are the only AR Manufacturer to build and test every single part and piece in house- no subbing out parts at all. That's a testament to their strict standards.
I understand what you are saying about handling a large volume of rifles from different manufacturers for sure. Even though they feel and cycle in a similar fashion, there are big differences when talking percentage of rifles manufactured to known issues/failures.
And most people won't ever shoot enough to push their rifle to the point of failure in the first place. Most guys aren't taking a single 2-3 day class a year let alone multiple classes like that Shooting 1500-2000 rounds in 2 day period, getting down in the dirt, driving the rifle hard- etc.
Most guys aren't over in the sand box either, sounds like you had a good armorer(s). That can make a big difference!
Biggest things I look for in a quality AR/manufacturer:
BCG: must be made from Carpenter 158 steel properly shot peened and have properly staked gas keys and MPI and HPT tested, no batch testing, but every single bolt carrier group tested
Barrel: Barrel made from the proper MIL-B11595-E CMV Steel, HPT and MPI tested with chrome lined 1:7 twist rate and a proper 5.56 NATO Chamber with M4 feed ramps
Cold hammer forged barrel is icing on the cake and definitely my preference.
Proper "F" front sight base and parkerized under the FSB.
Properly staked castle nut and an H-Buffer and 1.14" Diameter receiver extension.
You'd be surprised at how many companies out there do not build rifles to proper specs. Are they crap- NO- but there are differences in quality of materials, quality of construction and quality control/testing.
One company could even get the same Carpenter 158 steel from the exact same a metal shop, but have a different standard/QC for the shop to follow and end up with inferior metal.
I love talking guns, can you tell? :AK47: