Hi Decrypt,
You didn't mention if you already have an airbrush so I'm presuming this will be your first purchase.
For my 2 cents I'd start with an Iwata Eclipse 0.35mm and if you really want to try a dedicated detail airbrush get the Sotar 20/20 from Amazon as well (its very cheap so why not). Once you've used these airbrushes for a while and learned your skills and techniques you can buy a Micron if you think you need it. You can do without a detail airbrush but you can't do without a workhorse airbrush like the Eclipse, it is soooooo much easier to work with when you are starting out and you won't get frustrated like you will with the detail airbrush which tend to be very fussy about paint reductions.
I have an Eclipse side feed HP-SBS with is very versatile and I can do almost anything with it and because it is a side feed I can put different sized cups and bottles on it depending on how much paint I will be using. Heres a YouTube video I made on my Iwata side feeds
https://www.youtube.com/watch?v=UliSlSp_Y50
In this video I use the Sotar 20/20 and I'm showing how I corrected painting too dark
https://www.youtube.com/watch?v=k9iGd7P0DMI
I have an Eclipse HP-SBS, an HP-SB+, a Sotar 20/20 and an Olympos Micron and to be honest I really like them all but out of all of them the one I would miss the most would be the Eclipse, it's a fantastic all round airbrush that is very forgiving with paint. It will paint backgrounds as well as give you good detail. A dedicated detail airbrush is only really good for detail and you will always need a workhorse airbrush unless you only paint miniatures
If you don't want a side feed then the Eclipse HP-CS 0.35mm gravity feed would be the way to go.
If in the future you decide to stop airbrushing you can sell your Iwata airbrushes and get a reasonable price as they hold their value if they are looked after so don't worry about that. I made the mistake of getting an Iwata HP-SB+ 0.2mm in the beginning and it made learning more difficult till I got the Eclipse HP-SBS 0.35 and then I could really start to paint
This is just my opinion and you have to make up your own mind but for a first airbrush you can't go wrong with an Iwata Eclipse and it will last you an airbrushing lifetime. If you are in the USA I believe you can get a 40% coupon for Hobby Lobby that sell Iwata's and you could buy 2
Mr Micron knows more about that stuff so ask him. I would also look at Etac paints if you can get them.
Good Luck
Mel