Since you're not squirting metallic I would go with single stage. As far as a run/sag/orange peel its easy to fix by cutting and buffing. (For a run you take a new razor blade 90 degrees to the surface and scratch the high spots down flush and then 2000grit and buff.)
I've used a fair amount of Omni, while certainly not top shelf stuff, its probably the best value for the dollar. I will use it for certain projects as long as its still available.