For one, the B+W's are considered by many as 'better' than the Hoya line. You don't say what type of filter you're looking for...UV or CPL? For a UV (if you choose to use one), the B+W UV010 MRC is the one to look for if you decide to go with B+W. For a CPL, the B+W Kaesemann MRC (only because its priced about $10 more than the non-Kaesemann). You 'normally' wouldn't need a Kaesemann type CPL, but for the $10 difference its worth having (Kaesemann means that the filter is sealed to keep out moisture, also uses a better grade of polarizing foils).
Hoya and B+W are both good filter lines. Generally, in order of quality (according to some, but not sure how its verified): Heliopan, B+W, Hoya. In either case, no matter which brand you choose, be sure that the filter is multicoated. For B+W, its designated as 'MRC'. Not sure what the others designate since I use only B+W.
You already have the lin for hvstar. BTW...hvstar only accepts Paypal for payment. Other than that, they're a very reputable dealer...I use them exclusively for B+W filters.