I want top tier. I don't like settling for less. But what determines tiers?
How close it is to true "mil-spec".
I think sometimes folks forget that "mil-spec" is a MINIMUM standard. It is possible for an AR to not be "mil-spec" but indeed be built to an even higher standard.
That said, I mentioned Colt, Spikes, Daniel Defense, PSA, & BCM earlier because they are at least easily identified as being built of mostly mil-spec parts (with the obvious exception of the select-fire trigger). You at least know what you are getting.