The gas impingement system is an advantage due to accuracy. This is why the AR (given equal calibers) is the most accurate gas operated rifle. That is probably why they rule national matches. ARs with pistons, and there are a lot of them out there, are simply not as accurate GI ARs, nor have they proven to be much more reliable with carrier tilt being common complaint. You connect a reciprocating mass to a barrel and it introduces variation. Mechanical accuracy, to be fair, only generally leads to real world performance and there are a lot of variable to consider. I'm in favor of stacking the deck whenever I can.
The AR180 isn't in production as far as I know, and it was only available in 5.56/.223. It was reputed to be an accurate rifle, but it still has a reciprocating piston attached to the barrel. I can't tell how the forearm is attached to the reciever on an AR180 but I'm not sure it's a free float which could also introduce variables.
The greatest flaw of the GI system (jamming after prolonged fire) can be mitigated by using NP3 coated bolts and carriers, the right powder, and a little maintenance. The next greatest flaw is easily fixed with a caliber swap. The 6.5Grendel looks to be a fantastic round that compares quite well with a .308/7.62.