I've owned, sold, and still have a bunch of airbrushes. It took me a long time on my own to figure out what I wanted.
Ultimately, it is the same stuff the top airbrushers are using. I spent alot of time and money trying to find the "micron killer". The airbrush that could do the same job but much cheaper. There is a LOT MORE to an airbrush's performance than if it can spray a line. Finally I found a deal on a Micron cm-c plus, and never looked back. They are everything that the hype machine says they are.
Even airbrushes with the same specs, and even the same manufacturer, can react differently. My Iwata TR-1 will out perform my HP-C. Yet on paper they are almost identical. I have no idea why.
So once I found my holy grail detail gun, all I needed was mid range and large background/priming gun. Here's where things can get muddy and many many guns fit those slots. I'm a big fan of the Iwata TR series. I got a Grex Tritium TS lately and that has alot of really cool features. Very impressed with it.
I love having multiple airbrushes to keep color changes to a minimum.
I've seen pics of guys with 30+ guns... I might have been one of them.. but it finally hits you at some point, if you're not a T-shirt artist in a mall, then most of those brushes are a waste of money. I've been trying to thing my herd. For every airbrush that I decide is a waste of space, I end up buying another of my favorites.
It's a bit of a sickness.