Re: Gas piston Vs Direct Impingement?
I have put more than 10,000 rounds through my (DI) AR in the past 3 months without a failure... That means that in total that gun has upwards of 15,000 trouble free rounds through it. I'm not sure how reliable you want.
Right now, DI is cheaper than piston. As Nathan said, the piston operation hasn't exactly caught too much steam and is still fairly expensive.
In theory, the piston will run cleaner (which it does) and will therefore be more reliable. The DI system uses gas from the last shot fired to cycle the action and that causes more residue to be left in the action and entire receiver. If the gun isn't properly maintained (cleaned after each range trip or large volume of fire) then yes, it can cause a problem.
I, personally, clean each of my weapons religiously so there is mot a drawback for me using a DI gun.