I haven't used Heliopan, but I know of at least one professional photographer of renown who favours it. They're made in Germany, like B+W, and based on their price tag I would expect them to be top notch. Can't see you going wrong with them. They even have a polariser that has only one stop light loss. I'd recommend you to get a Kässeman-type polariser, especially if you'll be shooting in sub zero temperatures.