I keep the 9mm AR just because I can use Glock mags. But it is intolerably gassy with a can so I only run a blast deflector. Much prefer the Scorpion after a few mods. Most essential IMO are the HBI trigger spring kit and a longer charging handle. Both cheap upgrades. I also added a Magpul grip, duckbill mag release and CZ Custom folder adapter with AR tube and brace which totaled about $400 more. Much more pleasant to shoot with an Omega 9K than the AR9.