"I want an AR-15, which is best?" is really too vague.
What is the target, at what range, in what environment, for 85% of what will really happen?
Don't worry about the brand, concentrate on the features you need. "Can't have too many Picitinny rails." says a lot, the government supplier, KAC, has already said the quad rail IS too many rails for the average shooter. Who needs 48" of rail? The statement implies a lot of enthusiasm for a military look rifle without a corresponding understanding of why some things are included.
Sights vs. Optics is just one consideration. Look at all the hunting, varmint, and precision rifles out there, very few come with iron sights as backup. It's been common since the 60's to delete iron sights on scoped rifles as redundant and dead weight. If the AR is being used in the same way, the same reasoning applies - delete the irons. Grandpa did exactly that sporterizing the old 98K's and other milsurps, too.
Rather than just suggest a fanboy brand, figure out what's important and get the features you need:
Barrel length:
Matching gas action:
type of upper, flattop or carry handle:
sights and optics the upper restricts you to:
type stock that matches the barrel length and sights:
which handguard or free float:
trigger:
controls, if enhanced:
With selections made in that order, the gun sorts out pretty quick, and will be the optimum for what it's supposed to do.
You don't pick a 14.5" barrel for long distance precision shooting, and then slap a sniper stock on it, or go 20" for varmint, and add a CAR (which is actually pictured in forums more often than I can believe.) Select the features that match the job, not the fantasy, and do that selection keeping in mind what the gun does 85% of the time, NOT what you would like to stretch it to do the other 15%.
Put together all the 15% options in an all purpose gun, you get something that doesn't do anything well, and comes off looking like a cross between a dachshund and shepherd. Guns are built to meet tasks, not exist as a collection of primo parts showcasing a credit card limit. Too many AR owners don't see that, but they sure post up great examples of it.
What's funny is that the standard we compare to is a boring recipe of listed parts: Colt barrel, Colt upper, Colt lower, Colt stock, etc. Or swap Colt for FN. On the internet, tho, you get a list that sounds like a Baskin Robbins menu, and the game seems to be not ever doing a Brand Name supplier more than once.
Don't be one of those with more credit card than knowledge of what's really needed. Most of this stuff is designer grade anyway.