I'd say it depends on your budget, and what you already have.
On any given project, I usually will use three airbrushes, one for larger areas, one for the "middle work", and one for detail. Sometimes I'll use more or less, depending on the project.
For detail, if you've got the money, you can't beat a micron. I would probably go with an Iwata CM-C or an Olympos MP200-C, especially for automotive-type work. All of the microns are awesome airbrushes, though. They are expensive, but once you use one, you know why.
If thats too expensive, I would recommend something along the lines of an Iwata HP-B+. A bunch of companies make comparable airbrushes (gravity-feed, smaller color cup, usually a .2 nozzle or close to it). My personal favorite of these is the Olympos HP100-B. The Iwata HP-B is very similar, also of high quality. Grex's XN model is designed very similarily, as well, and they're well made, reliable airbrushes. The big difference between an Iwata and a Grex XN is in the material qualit Grex uses softer metals, to the parts, especially the needles and nozzles, don't last as long.
I like my H&S Infinity, as well, but if I was to buy it again, I would just buy the Solo kit instead of the 2-in-1 kit. The .2 nozzle works just as well as the .15, but is less picky about paint. I think I used the .4 set up that came with my 2-in-1 once, and that was just to see how it worked.
I haven't used a Badger Krome, but it seems like the people on here who have them like them. I tried an ealry version Renegade (same as Krome, but with the blackened finish) and thought it was terrible. But, it looks like most of the problems have been worked out with the Kromes.