As the owner of the HP-CS (which was also my first airbrush), I can say it's a great general purpose airbrush. It is easy to clean, performs well, durable, sprau acrylics, enamels and lacquers, etc. It's limitation is the needle size, of which mine is 0.35. Instead of investing in a finer needle and nozzle, I inherited a Sotar 20/20 which I use for mottling and finer detail.
If I were in your shoes, though, I'd probably go with the HP-B. The high performance line from Iwata is just that much nicer than the entry level Exclipe line. Not knowing you skill level, the HP-B might be overkill at first, but as you use it a grow with it, you'll appreciate it's ability.
I did notice that the cup size is smaller on the HP-B. This may or may not be a factor to you.
Either way, I think you'll be happy. Iwata makes a fine airbrush.