The LWRC and HK 416 are the only proven piston ARs. I wouldn't bother with the Ruger until its been proven.
From the Defense Review:
Defense review is crap, David Crane has little to no credibility whatsoever. He gets reamed on Lightfighter.net all the time. Here we have a civilian who couldn't hack an standard infantry unit touting himself as a legitimate specialist in SF weapons and technology? hahahaha. He is a GWB, Guy with Blog.
I used to be a Defense Review regular reader until I noticed that his blog is basically a rolling advertisement. The TAPCO fucked RPG and M-79s were some of the most blatant examples of how he'll whore himself out to anyone. Every now and then he is lucky enough to get someone who actually knows what he's talking about to write for him (Mike Pannone). David Crane himself though, has no credibility more than you or I. He's shot a bunch of demo guns in demo environments for companies who want a mention on his blog. Big whoop. How many articles has he written ENTIRELY based on pure, unadulterated speculation? Many. The recent round of HK416 rumors started with a single report by a Norwegian soldier posted on AR15.com... and then a Bushmaster sponsored firearms blog start saying the DoD was recalling 10.5" HK 416s without a shred of proof. David Crane thought it necessary to comment on this.
Anyway, the 10.5" HK-416 primarily serves the role of replacing the MK18 Mod 0, which can be finicky when switching between supressed/unsupressed mode. The piston operation of the HK-416 lets operators have a weapon that function reliable with, and without the KAC NT4.
However, even a broken clock is right twice a day, and Crane seems to be advocating strengthening maintenance of the M4/M-16. Which is exactly what any person with any experience with ARs and half a brain would say.
Unfortunately, the reality of Army Ordnance politics, and the fact that most soldiers aren't "gun people" means the DI system will continued to get blamed for jams that are really the result of poor maintenance.