If you have quality glass, like the Canon L series, then you need quality filters. the B+W are made from ground optical glass, not a piece of plain glass like as you see in the tiffen and hoyas filters (even the expensive ones are still cheap grade glass). Only B+W and Heliopan put the time and $$ into making filters that are designed to be used with your quality lenses and not distort and reduce the optical quality of them. I have a Heliopan as well, and I prefer the B+W a little bit more as its a brass ring and not aluminum and thus does not bind up as easy, and thats important when you want to change filters quickly! If you use a cheap filter on a pro grade lens, you are wasting your money, on the lens and the filter as the filter just hurt your image quality, and thus you lowered the quality of your lens! In filters, like lenses, you get what you pay for!!!
I shoot in all kinda of weather conditions, from sunny and warm, to windy and cold or snowy, and I have never had any major issues with any of my B+W filters acting up! I prefer the MRC, but even their entry level one is ground glass, so you still get a great quality filter at that price point.
You need a UV filter on all your lenses, as it helps to protect your front element, as I have seen many lenses saved when bumped or dropped by the UV filter. If you are outdoors shooting or around kids or food at all, you have to have a UV filter no matter what! The B+W does not degrade your optical quality from a quality pro-series lens, like a Canon L Series, where a lower grade window glass filter would, like all the Tiffen, Hoys, etc. Even the Canon filters are not ground glass, and thus why I dont use them! Just be aware if you are using good filters, you can't blame a bad image or blurry shot on the glass or filter then, you will have to own up to actually taking a bad picture every once and a while... :)