A couple of points.
One, SHTF doesn't exist. If you really need that gun, they issue it to you. And it could likely be an FN M16A2. Colt hasn't always done the job.
Two, picking a brand first means assuming it has quality. It very well does not. That changes over time, and on the open market, there is competition.
Three, the AR market uses the milspec standards for the M4 as a guideline, but you cannot possibly buy one. It's automatic Government use only. Whatever you get will be short of that, and only certified milspec if the Government hands it to you.
Four, since you must do homework to ensure you are really getting the quality you want for the money, you need to know what features are milspec, and who uses them. Then you have to ask if it's even relevant to your use. You CAN get better than that. Milspec is a minimum standard of construction to get the government what it wants, without cheating the taxpayer. It is NOT the ultimate technical standard or best way to make it.
Five, if you don't know what specs you are getting, using the price as a guideline is useless. Makers and vendors in the distribution of firearms do not pay exactly the same money for identical parts, and do not mark them up for the same profit. Government suppliers NEVER discount their goods, to protect their contract pricing - which means it's inflated to support their reputation.
Six, buying Brand or style of gun ignores what you will really use it for. It may be a cool SHTF gun, but lugging a Barrett .50 thru the streets of Katrinaville may not be the best choice. Examine what you need it to do most of the time - then choose the caliber and barrel length to do it. They are primary, not Brand, because that's what launches the bullet. An engraved name on the lower contributes nothing to the barrels accuracy or the ammunitions striking power. Case in point, if you plan to hunt with it, you may very well not be allowed to use a Colt, simply because 5.56 is illegal in your jurisdiction. Colt doesn't necessarily offer the best alternative caliber, and insisting on Brand at that point is useless. You can't have it in the caliber, barrel, or work to install it. It will not be Colt.
Seven, working through the process of matching the parts to the task means understanding milspec could very well not apply. That's where you have to discern quality, not hype. Quality is reflected in material selection, appropriate shape, and what testing it went through to show it met a standard - and what that was. Do you get a semi auto bolt carrier group, and live with it's lighter weight and that it cocks the hammer on the back of the firing pin, or use the originally designed full auto BCG with it's slightly heavier weight, and which cocks the hammer on the shoulder of the carrier that shrouds the firing pin? Have you read the pros and cons of both, or just willing to take whatever you get and live with it? Some did, and found Colt had seriously cut away semi auto carriers, and even used different sized take down pins, which complicated swapping uppers. It was not a simple pop the pins and switch.
Eight, since Brand, milspec, and internet recommendations cannot be trusted to get you what you need, it's important to realize that you could very well wind up with an albatross completely unsuited to what you needed to use - regardless that you wanted it. That's fine - if you want it, get it. Using firearms has some flexibility, and it's often a matter of degree, not being either capable or completely incapable. However, the emotional assessment of being satisfied will likely tilt one way or the other, and reservations or complete dissatisfaction is common. At that point, at least, some knowledge is gained - it's up to the individual to decide if it was worth learning that way.
Me, I studied on the AR for some time, reflecting on what I liked and dislike about it while using it for 22 years in the Army Reserve. It boiled down to selecting the caliber and barrel, then what upper would be needed, the optic/sights, furniture, and trigger, in that order. Too many approach it backwards, and wind up with a $1200 wonder rifle that still only shoots 2MOA, and can't do better. In that regard, it's milspec.
If you want better than 8" groups at 400 yards, you don't get milspec barrels and assume they do it. Don't get suckered into the trap of Brand or spec, select features that meet the goal.