I have experience with an airbrush and IMHO it is great for full body repaints. I also use the airbrush to touch up or fully repaint blush on a pony's cheek. You can also use the airbrush to create interesting effects on a pony, such as a gradient.
I used a regular paintbrush, with much success for full body repaints for a long time, but the airbrush gives a finesse I couldn't get any other way.
It depends on what you want to achieve
Love pkw xxx