When I was still working, our preventative maintenance foreman toured a Wix filter plant. What he was told during the tour was that Wix makes privately labelled filters for others to their specifications. When our guy asked if that meant some are better than others, the factory rep just smiled and repeated that they are made to the customer's specifications. Take it for what it's worth.
Makes ya wonder what the media difference might be between standard Wix filters (say the 51515) and the Napa Gold equivalent.
