What are you wanting to paint??? As many will tell you, the fine line is achieved by controll of the airbrush...however, the smaller the nozzle, the easier it will be. With that being said...two things that would concern me...1) bottom feed...I have a badger 155 and do mostly illustration...the siphon feed, or use of a bottle or small cup, is a pain in the butt. Yes I can mix large amounts of colors...but I find that I really don't use that much paint to begin with...and if I do, or know I will...then I mix it in a bottle and pour it in the little extra cup (I hate the thing, but the bottle is just as bad...and I think the paint has to be a little thinner, or turn the pressure up slightly. 2) the HP-C has a .3 mm nozzle while the BCS has a .5 mm nozzle...usually, the smaller the better at getting a fine line.
Now with all of that said, I have a badger 155...and I am able to get pretty clean thin lines (about 1.5x's of a sharpened pencil) with the right pressure and the right paint thickness...but it has taken tons of practice, and I still mess up on occasion.
Here are the links to Iwata-s website:
HP-C --
HP-BCS --
You can also click on "product usage" on the page and it will tell you how well it works for what you are wanting to do...notice, for illustration, it is not recommended...