Personally, I prefer using acrylics...non toxic, easy to clean, can thin down with water, mix well, and they are very flat. But I'm a big fan and proponent of mixing to get a desired color and tone. Favorite brand to work with through airbrush, Testors Model Master Acrylics) surprisingly. Favorite brand to work with topically, (Humbrol Acrylics) also surprisingly. I love Pollyscale colors but they are absolutely a headache using for airbrush. Maybe because they are discontinued and all the stuff I have is New Old stock, but everytime I use it in my airbrush, it clogs up because its so globby, even properly thinned and even if I try and strain it, some small pieces always find their way lodging into the nozzle.
As for archive-x, they are very appealing with all the research being done, but unfortunately they are moving very very slowly on the Fett Helmet colors. And to reiterate what has been said above, some members have been using (non archive-x confirmed) colors like 1975 light green as the dome green with misted grime. The results have been good but not great. If only they would do an acrylic line, so far I haven't had the desire to go enamel.