I myself hold a British passport and Hong Kong passport and did extensive research on this a while back as well as talking to other people in my position who are frequent travelers. Coupled with personal experience, I can tell you: get the Hong Kong passport.

There is absolutely no reason not to get one. The HK Government has been pushing for the HK passport to become more recognized around the world, and it has been working. Simply take a look at the number of countries & territories that accept the HK passport for visa-free travel.

Compared to other passports, even a 48 page HK passport is much, much cheaper. Even when traveling throughout the European Union, I use my HK passport simply because I have seen through different incidents the protection offered by the HK government to its own citizens. Contrary to whatever the politics maybe, it is different from China and special care is given for HKers.

Besides, what is a HK$500 investment for a 10 year, 48 page passport that will offer you visa-free access to certain places EU/US passports cannot go and give you a peace of mind? I understand the attitude in 1997, but in 2012 I always advocate family and friends to renew foreign passports to retain citizenship but get a 48 page HK passport and use it as your main travel document.