Re: LWRC spartan II or KAC SR-15
I have had an Adams Arms upper (same basic piston design as LWRC) and have owned a SR15E3 and now own an SR15 Mod 1.
You're right about shooting suppressed. Most of the gas will be ejected forward of the barrel and not into your face. With my AA, I noticed the same kind of standard accuracy as any other high quality AR15 with the right ammo.
The SR15s come standard with the URX bolt, ambi safety, mag release and bolt release. The newer ones have a tighter upper to lower fit but I've read about more QC issues on the latest guns. Mine included. They also come with the KAC 2 stage trigger, which is very nice. I shot an Accuracy International AE today and if I were blind folded, and they were both in the same stock, I wouldn't be able to tell the difference.
I choose KAC not only because it comes with everything from the factory and there's only one company to blame should something go wrong. But also because of the balance. If you shoot a piston gun for a day then switch to a regular contour barrel ar15 then switch to an SR15; the difference is amazing. I added a Battlecomp 2.0 and Vltor A5 stock. It literally shoots like a .22lr now. My friend laughed at me because I rattled 10 shots off easily within a couple seconds and all landed where I wanted them. He thought I was just screwing around until I had him do the same thing.
If you're going to always be suppressed, I'd go piston. But if you'll be unsuppressed at least 50% of the time, take a real good look and feel at the SR15.