Ok so I have the cash right now to buy most AR's on the market - stag, DPMS, rock river, Daniel defence, NEA, colt
My perspective on the brands you listed:
1) Stag. Have owned a couple and have used a LOT of their parts for custom builds. Honestly, I have NEVER had a Stag part not fit or work right. The only bad things I can say about Stag are that I dislike Wylde chambers and like almost all US-made AR's coming into Canada right now, stag has a Wylde chamber instead of the (now evil) 5.56 chamber and that on SOME models, Stags have at times had the flash hider pinned and welded on for State Dept. reasons. Also they use YFS brand screws on their bolt carrier gas keys. I've never had a problem or issue after using MANY Stag BCGs in builds (my preferred brand since we stopped getting Colt) and have never had a problem. Most haters just dislike a taiwanese screw on a US-made part methinks. Verdict? Buy with confidence. Greeat Canadian lifetime warranty for original purchaser too.
2) DPMS. I don't think you can currently buy a DPMS AR15 in Canada, though you can buy their .308 AR and you can buy Remington and Bushmaster which are now all owned by Remington and those brands now mostly use DPMS components. DPMS makes AR's in more than one quality tier, some of their stuff is bargain made and bargain sold, some of their other stuff is top notch. I have and will continue to use some DPMS parts, but you need to know what you're buying. I regularly use their detents, springs, disconnectors, selectors, end-plates, gas blocks, gas tubes and roll pins. I avoid their castle nuts as they are not stake-able, I won't use their receiver extensions as I've had them be out of spec in the past, I don't use their hammer/trigger pins since you can get better ones for the same money (at the same price point Hi-standard pins are a good choice) and I'm not a fan of their hammers because they sometimes come with poorly ground notches, but if you need a radiuses hammer you often end up with DPMS. They can be stoned back into spec generally if you know what you're doing, should yours not be a good one. Their barrels CAN be good if you get the right thing. In the 14.5" market, their AP4 barrels are made for LEO Contracts and are pretty good, but are 1:9, not 1:7. Be aware before buying. Their AP4 barrels have always worked well for me and are an excellent buy from Wolverine at around $250 including A2 gas block.
Rock River: Honestly, the only RR parts I've ever used were an ambi selector and a commercial diameter buttstock kit. I have also used their 9mm BCG and 9mm hammer. These parts worked well - but I've never owned a complete RRA AR.
Daniel Defense: Never owned their ARs, but have test fired two. They worked well, but this is a small sample size. Fit and finish was a touch below Stag IMHO. After running both a DD bolt and Stag bolts, I prefer the Stag which is generally better made from (IMHO) better materials (machined vs. MIM cast gas keys). Buy with Confidence, but if the price is equivalent, I would go Stag.
NEA: Never owned a complete rifle but have used their parts. Price-wise, these are worth considering over a Norinco - absolutely. They have a lifetime warranty in Canada with non-US parts sources throughout which is a good thing in terms of continual availability not dependent on the good graces of the US State Department. I have used the following NEA Ar parts in builds (to date): Upper Receiver Parts Kit (no issues, worked great, as nice as any I have used), Lower Parts kit (mostly functional, but the disconnector was crap, the hammer had to be stoned to fit and work properly within acceptable trigger pull ranges and the hammer and trigger springs were totally out to lunch and had to be replaced. The detents are functional, but are blued non-GI type with detent tip on only one end. I swapped mine out for proper double-ended zinc-plated detents made by Armalite - my understanding is that newer LPKs are much better with new springs and better hammers), gas tube (worked great), flash hider (worked great), pistol grip (worked great, but I prefer Colt-style thicker A2 grips). I also fired a couple complete NEA's at the range and they both worked flawlessly (a 14.5 and a 10.5) and both were of more recent manufacture. One had a gritty trigger, but everything else was fine. The trigger could have been fixed by stoning.
Colt: The only issue I ever had on a Colt (I've owned 2 SP1's, 4 AR15 "sporter" models - mostly HBARs, and a 6920) was that on one HBAR the flash hider was mis-indexed from the factory. A 2 minute fix. Colts run very well and are the only AR on the civilian market of which you can be 100% assured of compliance with the US DoD M16 or M4 technical data package. Some exceptions are the models made specifically and purposefully with oversized action and DCG pins, C-cut bolt carriers and sear-blocks, but that's all stuff that does not affect function in general. Buy with confidence if we ever manage to get new Colts imported again. Oh, and in general, Colts are overpriced for basic models.
Those are the only brands you mentioned, so I won;t comment on others.
