I don't have comparative data as I've only used theKäsemannCPL - but I can tell you that it's very nice! My logic was exactly as barba suggested - in for a penny, in for a pound. It's already an expensive filter (I'm not a fan of cheap filters on good lenses!), so I spent a little extra for their top of the line CPL, and got it in the slim version (since I keep B+W MRC UV filters on my lenses, and there are occasions when I don't have time to remove the UV and screw on the CPL, and just stack them instead).