Single action airbrushes are easiest to use. But you may outgrow those too soon.
I'd recommend a quality dual-action, internal mix airbrush with "metal" type internals (Aztec has airbrushes with plastic internals). Once you get to this point, selecting a dual-action internal mix, it comes down to personal preference.
I've been using an airbrush for some 24+ years. I've had many different airbrushes. Currently I have 2 Iwata HP-Cs and a Paasche VL.
For painting lexan bodies, I've only needed to use my VL. The VL does it all from thick to thin, from fine lines to broad lines. It can handle it all. The price is also right. Bear-Air has the "kit" for around 60-70 bucks.
Although this is what I use, again, any quality dual-action internal mix would fit the bill....