The JM pro version is what i just replaced. Its a good gun to get started in 3 gun because its ready to go out of the box.
IMO the gas system is not very reliable and very picky on ammo. That is just my experience.
If you want to get serious about 3 gun like, I have decided too, you need to have equipment that is as close to 100% reliable as possible that is why I made the switch I was tired of dealing with issues with the shotgun.