Hrm... in my experience, a DI system is perfectly suitable for most civilian use. I would only get a piston system conversion for a rifle that is probably going to be fired ALOT alot, unless it came part of an affordable package. Most piston systems, unless you convert them, aren't especially affordable.
That said, I'm eyeballing the Ruger SR-556 variants. I don't really need Mil-spec, I've got 2 Arsenal AKs for that, and I hear they're quite accurate <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
I guess it depends on how you intend to use the rifle. Is it going to be a plinker, maybe a couple hundred rounds in a session, then cleaned as soon as you get home? Or is it going to be a toss about in the mud/sand, Class III lower (<img src="/ubbthreads/images/graemlins/grin.gif" alt="" /> probably not though...) Sound suppressor (gas blowback into the action from the change in pressure), hundreds of rounds between cleanings in the sandbox? Granted those are both fairly extreme ends of the spectrum. Sure, it'd be a bit easier to clean than a DI system, but unless you're burning the rifle out every session, even a DI system isn't that hard to clean. It's when a large amount of ammunition has burnt the carbon onto the internals that it becomes a PITA.
Personally, I've never had any issues with a DI system, even in my military issue weapons. I ran my M16 hard in basic, blanks, live rounds, those little blue plastic rounds that gum up the barrel when it gets hot, you name it. I hardly cleaned it except for a wipedown of the internals and a good oiling every day or two, and it had no issues (canted front sight base being the exception.) I did scrub the bore occasionally, but in basic time to scour my rifle was short <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
As far as recoil a SSGT from my unit, and a friend of mine, owns a LWRC piston driven rifle. Comparing to one of his standard ARs, recoil is still negligable (it's a 5.56, lol), but the impulse feels different. The front end is heavier, so it's not as pointable, but honestly the difference isn't noticable. Not to me, anyway.
