1. Figure out what ammo you plan on shooting. Not all AR-15's have the same twist rate. This make a big difference.
2. Figure out what accessories you would want to put, what furniture, sling attachments.
3. Fixed front post? Flip up front sight? Do you want to absolute co-witness, lower 1/3? Red dot only? Magnification?
4. DI or piston?
I was in your boat. I went to several shops and help a bunch. One of the Armalite triggers I tested was the worst I have ever tried. I decided on needing a 1in7 twist for shooting the 77 grain SMK's (I only handload). If you plan on shooting a lot of 55 grain or around there light stuff, you may want a 1in9.
I wanted Mil-spec or close to it, light, flat top, good sling attachment options, tight upper to lower, fixed front post, tight tolerances, ready to go out of the box, $1300 ish, 1.5 MOA or better with handloads, and Magpul furniture. I wanted warranty, one that isn't a new company that could up and vanish in a few years. I wanted gas not piston as that is what I am used to from the army, it is simple, reliable and unless you are shooting a lot a lot without cleaning DI is fine. The really good Piston AR's are really expensive, HK, LMT etc.
So all of that narrowed it down to the M400 Enhanced or Colt for me. I went with the M400 (no guarantee on the accuracy but from most reviews I should be able to get it with handloads). It should fit my needs. It is in the mail or I would tell you how I like it. I suspect I will be changing out the trigger one day but we will see.
There is no right answer. There may be a dozen AR's you'd be happy with.