Airbrush:
Single stage is great for base coats,or volume work (a lot of one color). Not as much control over the pattern.Need more pressure as they work on suction,sucking it up from the bottom..
Dual Stage:Great for detail work (scales,fogging,eyes,spots,shading).Greater control over air/paint mix.Uses less air pressure as it's gravity fed,from the top down..
I use Iwatas. I use a bottom feeder to to blow on base coats.Then come in with a top feeder for detail work. Lots of times,I'll do a bunch of a certain color combo to eliminate cleaning /changes.
My advice,get a Michael's coupon for 40 or 50% off one item.Pickup a bottom feeder and get the hang of it. You'll also need a compressor..Airbrush compressors are like pissing in the wind..Get a pancake or twin stack compressor. Airbrush compressors run all the time (no storage tank). Real pain in the balls and noisy...