For rockets, where broad area coverage is the main use, single action is easier to deal with. They're typically easier to clean, and with a properly sized nozzle, they can give you coverage volume that betters most all spray can paints.
If you want to do detailed work, fine-line work, etc..., then perhaps a dual-action unit will be appropriate - but I find that's relatively rare in the world of rockets.
Paasche H is the old standby in the single-action category.