Actually there is little design similarity between the AR-180 and the AK.
The AR-180 used an impinging gas piston, same as the FAL. The gas piston slaps the bolt carrier and drives it back. Different type of operating system than the AK piston/carrier arrangement being actually connected and going back and forth.
As for internals, the AR-180 used and entirely different set-up than the AK and the parts were stamped from steel. The AK uses milled parts, and of course they are different in the way they work.
About the only real thing that is similar between the two is they both use stamped steel receivers.
That being said, I used to own a pre-ban Sterling (before the ban) and I liked it far more than the AR-15 system of operation. It was well thought out and a better system. The plastic parts sucked big time, but plastics back then sucked all around. The buttstock arrangement was bogus as well, but I still think it was a better design. Not asying it's a better gun than the AR-15, it didn't have years of development by the government at a cost of millions, but as a desgin it was a better starting point than the AR-15.
I think it would have been as reliable as an AK had it been developed. Unless a government actually takes the time to pour money into a system to evaluate and fix it, it usually will not be as good as one that has had that advantage.
The one advantage I can think of that the AR-180 had over the AK is that the bolt carrier runs on rods like the M3 Grease Gun. The carrier itself doesn't touch the upper at all. You could have an ungodly amount of crap in the gun and it would still work. As the cocking handle was fixed to the carrier, no AR-15 fwd assist thingy required. The AK has to run on rails in the reseiver. Obviously it works well, but there's a tighter fit there than the AR-180
In the end I'd say the AK would have the advantage because it's been fully developed.
Ross