I was looking to purchase the AR-7 earlier this year, but once I got to the shop and held both it and the Papoose my mind was made up immediately. I went with the papoose.

There was a small piece of plastic (nylon, whatever) for the alignment of the barrel for the AR and on the display model I could see that it was already heavily damaged. I figured if it couldn't handle in store use, I didn't want it in the field. When I held it, it also felt really nose heavy and frankly the stock felt cheap and bulky. It was a black model and the finish was gouged already as well.
The stock is not watertight, meaning while it will float (there are airpockets molded into the stock), your ammo will still likely get wet.

The Papoose aligns with steel on steel. No stock storage, but the case holds alot. I picked up a second 7 shot clip immediately for it. My understanding is that in the case the Papoose will float (assuming you aren't storing tons in it). The sling mounts are nice. I picked up a set of quick releases, and threw together a nylon web sling for nothing.

I have tried out a few brands of shells in it. Federal eagles were garbage and caused many jams. The blue box federals were only slightly better. I have had great success with Remington Cyclones and I assume the solid point Thunderbolts would be the same. Not a jam in a brick of 500, 3 misfires I was able to pop off with a second try. Tried some old standard ammo, shot nice, but not enough punch to fully load the next shell. I assume the Remington Goldens would work quite well too. Did try a real old box of CIL (probably 30-40 years old) High Power shells and they also worked great. I have noticed a slight increase in the tendency to jam if you put pressure on the clip with the front hand while supporting it. If you are getting a scratch on the lead of the next shot then that is what is happening.

Put a Tasco rimfire 3-7x scope on it just over a week ago. It still fits in the case, just, lol. I haven't had alot of chance to do much beside a basic sighting, but my brother used it last friday while I was sighting in my 308. With a life size rabbit target at 100 yards, using the sling, sitting on a bench,he could put a whole clip of 7 shots into it's head. He also hasn't done any shooting in 16 years. I'm assuming it would group very nicely if I had a rig to test it on.

My final verdict, and this is really just my opinion, is that the AR seems to be more for the guys that like to look like they can survive (an accessorie), but the Papoose is a real survival tool.