I think you would be hard pressed to see any difference between top of the range filters from either B+W or Hoya. For what it's worth, I opted for a B+W for no better reason than I liked the presentation on the Schneider Optics website (http://tinyurl.com/27mz89
) - check out their FAQs. Tom would probably be able to point out a similar resource for Hoya.
For day to day use I would certainly recommend using such a filter simply to mechanically protect the much more expensive glass it attaches to. If you suspect that a filter is causing problems in a difficult lighting situation it is only a moment's work to take it off and check. Has anyone ever had to do this?