Mr. Micron has a great point, and I agree 100% for your first airbrush you really do not want a trigger. If you're a hobbyist or into fine art something like the iwata eclipse hp bcs or the badger anthem are great brushes, the smaller needle size is great for fine work but these guns still allow a large spray area for gentle hazes or large area covers. ( Large being relative, canvas size or tee shirts).
The difference between bottom feed "syphon" or top feed "gravity" varies from gun to gun. But as a rule gravity fed non trigger guns like my richpen are used for ultra fine detail work, like when I paint on cars or motorcycles. The syphon fed guns require a higher psi to suck their paint and atomize it. So that higher psi makes it harder to work on less forgiving surfaces like metal, fiberglass or plastic. My guns ( iwata eclipses) spray well at 50-60 psi. Where as my richpen because it's gravity fed and doesnt need to create the vacuum can spray at psi as low as 15 or 20. And of course colors are MUCH easier to change in syphon fed guns.
So unless your doing a lot of automotive work id go with a bottom fed DOUBLE action gun. Double action being the most important thing... ever.
Also, i have 15 iwata eclipses, only one richpen. I can get the exact same detail on canvas or tee shirt with both guns, i can't get that same detail on a car with the iwatas. It all depends on what you're painting.
