Is there a huge difference in quality between brands of filters? I see/read comments about B&W and Nikon filters, for example, but can't find any real review or comparison.

Thanks for any input.

You get what you pay for in filters...
CPOLs or ND filters -> Nikon, B&W, Hoya Pro-1 line.

I got a B&W MRC CPOL. It's nice.

Difficult question to answer! A high quality filter DOES NOT guarantee excellent results and polarizers come to mind.
You do not have to spend a bundle to get great results. I trust my old, single coated filters of the 70's and I am very happy with my pictures. I like American made Tiffen polarizers and I consider them neutral in their response to color. I also use Hoya, single coated and multicoated and NO, I do not see the differences. I have no experience with B&W or Heliopan. Lee and Singh Ray are very good and very expensive.
As long as you stay with a known quality brand you should be OK but let that "difference in quality" aside, buy a medium quality filter and enjoy. As long as you keep the filter clean, the sun not striking the filter and most importantly, as long as you know how to use it, those filters should serve you well.
William Rodriguez
Miami, Florida.

thanks to both of you