The reason my first preference is Colt is partly because of several years of experience with them that's been totally reliable aside from one incident where I jammed one with a bad reload (my own mistake, too much lube on the pad, too much lube on the case in the resizing die, partially collapsed shoulder I didn't pick up on before trying to chamber it) a long time ago. Also base my preference on gunsmith opinions. Colt seems to maintain the best overall quality in materials and construction & attention to specs.
I see a couple posters advancing other brands while saying theirs is "not 100% reliable" and "but not so reliable". No offense to them, but I want better & get it with Colt.
Other brand commentary briefly:
For the last few years before I retired I carried a heavy 16-inch Bushmaster upper on a Colt lower at work. My gunsmith warned me I'd be likely to have problems with the upper being out of spec based on his experiences with the company & its products. When he inspected it the first time to certify it for department use, he found it was in specs & was moderately surprised. In the qualifications I went through with it, never had a single problem. That said, there was another agency locally that gave up on several Bushmasters due to function problems, and I've heard of reliability issues from other sources. My brother-in-law (currently retired) noted during his tenure as firearms instructor at the Salt Lake City PD that several Bushmasters would work fine at first, then began to develop functional problems over time at training sessions. I'm also hearing of broken Bushmaster bolts on other sites. I've removed my Bushmaster upper & retired it. It may never develop reliability issues, but I'm not taking the chance. This is not saying that every Bushmaster will be or go bad, just that their ARs have something of a spotty rep for reliability.
Next best, in my opinion & others, is a DPMS gun. That company started out contracting mil-spec parts for the government, and their specs are still good & pretty consistent. I've used their left-handed AR before with no problems, I just bought one of their lowest-priced entry-level 16-inch ARs (but have not had time to shoot it yet). DPMS has one of the most extensive AR lines along with accessories & options in the business. One excellent feature about that company is that you can mix & match their uppers & lowers if you don't like a particular combination, buy parts to upgrade with, or essentially build your own custom gun, and everything is built to match up with everything else because it's all coming from the same source.
I tried one Rock River upper with their two-stage trigger in one of my Colt lowers, it developed a tendency to try to go full auto & the trigger pull wandered down to about a pound before I gave up. I'm not saying RRs are bad across the line, they do have a following.
Olympics have always been their own game on specs, machining, materials, and quality. I would not bet my life on one.
I've had no experience with ArmaLite ARs in .223, but have tried two different ArmaLite ARs in .30 caliber that flat would not feed reliably. I've not heard anything negative on their .223s, and I'd assume those would probably be good.
I've tried a high-end Les Baer Thunder Ranch Model, and would have bought it had I had the $2500 it cost. It was the best built AR in overall quality and function I've shot, but with the general sense I get here ("I don't wanna spend much."), I doubt that would be a consideration.
Any time somebody asks "What's the best?" the answers will vary widely. I don't tell anybody what's best, but I do have my own preferences based on my needs, experiences, and info from people inside the industry. My ARs are expected to defend my life if necessary. Colt is not perfect in either customer service or meeting the customer market, and every company puts out an occasional lemon, but in my mind my chances for consistent quality and reliability are better with Colt and DPMS. The materials will be better over all, the parts will be closer to mil-spec (where that applies), heat treatment will be more consistent, tolerances will generally be better, and so on. I don't own Colt ARs for the name, I own them for what they give me. Colt has its problems in other areas, but the M16/ARs they put out are still well done.
The new S&Ws will probably be pretty good, time will tell.
For range toys, it doesn't matter, but my ARs are not range toys.
Everybody has their preferences & reasoning, those are mine.