Hi, Noah -
Don's airbrush site is especially informative, I believe it's the very best source of useful information. The Badger 155 Anthem is his favorite, and he has MANY airbrushes in his collection to choose from.
I have several different brands, Badger, Iwata, Paasche, Testors and Binks. They all produce good results, but as is human nature I have settled on Badger as my most used. Reasons? Low costs, extreme durability, and if parts are ever needed they are very inexpensive.
The issue of siphon fed versus gravity is just a very insignificant factor, some like one type, some like the other. For me I favor the gravity type, I find it just a bit easier and faster for cleaning when finished. On the other hand, my first 40 or so years of airbrushing was with exclusively siphon fed models, and I got on quite well with them.
Probably 95% of my airbrushing is done with two Badger models, the 100G and 100LG. Identical gravity models, the only difference is the cup size, the LG being considerably larger. You'll find the 100G reviewed at Don's site, if you're at all interested. One of the benefits is the ability to cover the bases of fine, medium and large spray applications, by a simple parts replacement. It only involves the needle and the front bits, the parts swap is done in just a minute.
For purchasing, I recommend USA Airbrush. I have made several buys from them, faultless service and low prices. Best of luck with your search.
Patrick