I am aware that the consensus is that B&W, Heliopan, and probably Hoya make the best quality filters. Schott glass in the German ones, brass mounting rings etc. Tiffen would seem to be, at best, an also-ran. Laminated, I think, possibly subject to de-lamination, although I have never seen this happen.
Ctein, in his book Post Exposure, found he could not see a difference in image quality when using Ilford VC filters below the lens. While this is a somewhat different application, the filter, in this case plastic, is between the lens and the 'film'/paper.
Has anyone run tests, or does anyone know of any information that indicates an inferior image when using Tiffen or similar filters. On the faceof it, B&H are certainly better. But is there a detectable difference? Given the difference in price and the number of filters I have/want/need I am wondering.