Speaking as someone who just yesterday bought his 4th!!!! airbrush and feels that finally, maybe just, he's this time made a good choice
I would recommend going for a double action.
The cost isn't that much greater (especially when you put it in the context of all the other associated costs such as compressor, spray booth, gas mask etc.)
The double action will goive you some flexibility of use that you are sure to be grateful for at "critical" moments at some point. Also, don't try and save on your airbrush - you probably won't be happy with it. It's better to wait, save up some cash if neccessary, and then get a really good one for more money (assuming that you will want to be using it for many years)
HTH - but you'll ge a million different opinions, anyway
