Choosing your airbrush really is a 'Horses for courses' kinda thing.
If you know someone with an airbrush, then see if they will let you have a go with it. Or maybe your local hobby shop will let you test one out.
No harm in asking.
Peronally, I have used an Aztek, and currently own an Omni 4000.
The Aztek served me loyally for years, and I still have a bit of a soft spot for them. But I wouldn't purchase one again, the quality appears to have slacked off a bit from what I hear.
As for the Omni 4000, it's a wonderful airbrush.
She does all the fine lines I need, wide patterns, and is dead easy to strip and clean.
I ordered mine with a Teflon needle bearing, so I could use it for Acrylics, Enamels and Lacquer based paints.
All airbrushes can spray acrylic and enamels, but it's the lacquer based paints, like Alclad II, that damage rubber seals, this is something to look into when your choosing.
I plan to get an Iwata soonish, just for the more detailed things like squiggle camo on 1/72 a/c.
Thats all I can advise, as they are the only airbrushes I have used.
IMHO, the Omni is a decent all rounder, and cheap, yet still has quality manufacturing and really good back up service if required.
Probably doesn't help you alot, but there is a guy here called Mike V, he is the guru for airbrushes on this forum, so you might want to hunt him down.