Armalite makes some good rifles, but I believe that STAG's are a little better made. Their parent company is a military contractor and provides many "mil-spec" parts to Colt/FN for use in true M-16/M-4 rifles. They also provide many critical parts to other AR "manufacturers" like S&W, etc...who simply rebrand and offer them for sale. For that reason, and from personal experience, I'd put the STAG rifles near the upper tier of modern civilian ARs. Not quite in the same ballpark as Colt/LMT, but nipping at their heels.
The current Armalite product is a good one, but not quite as good as the STAGs I've owned/handled. FYI, the current Armalite company has not connection to the original Armalite, makers of the AR-10, etc...back in the 60s. The current company bought rights to use the name, doesn't make 'em a bad company though! I've owned Armalites and liked them very much.