In m experience the V1 performs slightly better in cold weather and it's much easier to adjust the FPS if you need to run near field limits. Otherwise the V2 seems like an improvement in consistency and durability.
That piston is stock, but the piston seal is aftermarket. Likely a falcon.
In my personal opinion the gun is both more efficient and more consistent with a shorter barrel. It just doesn't perform well when you have to choke the gas system way down to get it to a fieldable FPS.