in AR15s, the DI rifles are more reliable. they were never designed with a piston in the first place. the gas piston AR15 was the answer to a question that was never asked. people didn't like having to clean their AR15s every several hundred rounds so they started slapping on AK47 style pistons onto their ARs so that they didn't foul with burnt powder as quickly.
this type of arrangement is not such a bad idea for military rifles but it's horrible for civilian application as a piston requires a very specific amount of pressure from the fired projectile to actuate it. since the military only uses 2 or 3 different loads in any given caliber and most are within very close proximity to each other(pressure wise). this is not a problem. however with civilian use there are dozens of different factory loads on top of the infinite number of hand load possibilities. if the pressure is too far out of spec your piston will no operate and you will effectively have a bolt action AR15 requiring you to operate the bolt manually. many civilian piston kits nowadays have adjustable gas systems to compensate for this but you have to keep a log of what setting works best with which ammo and the first several shots out of any new brand are going to be trial and error, trying to find a setting that functions properly.
me? I can live with cleaning every few thousand rounds... my gun never jams and It's never been cleaned in the 4 years I've owned it.
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
I never said half the stuff people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin