A lot of complaints about functioning issues with AR15 pistols. I bought both my complete uppers from PSA and they have been 100% reliable so far.
One has a 10.5" barrel and the other an 8.5" barrel.
Lots of complaints about noise from an AR15 pistol. I have "flash cans" on both of mine. A Noveske Pig on the 8.5" and a (darn, never can remember the name) cheaper version on the 10.5" pistol. When I'm shooting them I can't tell the difference between them and any magnum caliber revolver.
Both of mine have H2 buffers in the tubes, standard carbine springs, back up sights (which work surprisingly well considering how far out from my eyes the rear sight it when shooting it off the bench - like a pistol) and red dot optics. One has a DP PRO on it and the other has one of the advanced red dots from Primary Arms (that 50,000 hr. battery life thing really appeals to me.)
Same lowers, same uppers, same lower parts kit (with the exception of the butt stock if you buy the bigger lower parts kit by mistake).