AFAIK its not really the plastic itself thats the issue, just the overall filter when compared with the Racor made AC Delco.
The Napa/Wix has a Nominal Micron rating of 7 while the Racor is 4.
The Racor is also supposedly better at removing water than the other filters. It does use a coalescing media and I cannot find if the NAPA one does or does not. Napa simply says it has a paper element. The coalescing media is needed to remove the water from ULSD and Bio fuels. Its found in the factory filters on many modern diesels.
I trust Wix/NAPA Gold filters for most everything and use them as my main filter source for the farm and our equipment. Theres enough circumstances where I will use a different brand or OEM filter over the NAPA though. Some things that are under warranty its just one less thing to worry about should there be a major warranty issue, some filters where the quality is noticably better and the price is reasonable (many CAT filters), some filters where the NAPA price is higher than the OEM filter price (Allison), and the filters for the Euro cars, I choose to use MANN instead of NAPA because they are basically the same price and are very good quality.
As a general rule of thumb though, if I had a life and didn't micro manage little things so much like I do, I would just use all NAPA Gold like I used to. Its very nice just having one brand on the shelf if possible. They are not always the cheapest filters when compare with some other aftermarket brands, but they are a quality filter. I didn't have many issues with them when I used to use them on trucks but every once and awhile one wouldn't thread right, or wouldn't seal.
In this case though, I use the AC Delco TP3012. I don't feel it will cure cancer like some people seem to, but I do feel/suspect it is a better filter. It's not much more than the NAPA filter so its not a big deal to use it instead.
