I just want to share my experience at my LGS when I was choosing my 2nd store bought AR. When I went their to test the current AR's on the market (back in May-June 2016) I owned, and still do, a Sport I with the 5R barrel that was (4.5) years old. I had built a few AR's in the past, but, wanted a new, updated, current, store bought AR.
The Sport II that I had rented was very sloppy. It had been shot A LOT with very little attention to PM! The upper and lower were very loose fitting. The first day I rented it, the rear pop up sight would not even pop up! I took it back to the counter and they installed a new one. While I was there, I asked counter dude if I could exchange it for another Sport II. He said they were all (4) rented out. So, in all fairness, had that Sport II not had been in such bad shape, I would probably own another Sport instead of the current Ruger AR-556 that I chose.