What kind of oil filter do you guys use?
Here is at least a study with some testing rather then just cutting them open and taking pictures
http://www.gmtruckcentral.com/articles/oilfilterstudy.html
Yes, it is some testing.
And the author goes on to admit that it's extremely subjective and is no way comparable to standardized SAE testing.
But, then again, all the arguments in the world on this subject are extremely subjective. Oil filter brands, just like the brand of oil itself, for the most part is subjective. Everyone hates on one brand or the other, and everyone loves on one brand or the other, without being able to truly give out a response that isn't based on emotion. It's exactly what the manufacturers want and the gimmicks they employ to market the product.
I've had good luck with this brand. Someone else has had good luck with this brand. Someone has had bad luck with the brand I prefer while I've had bad luck with the brand someone else prefers. See the word "luck" being used in a lot of these discussions.
When a customer asks me which filter brand I prefer when making a recommendation out of the ones we sell, I "prefer" Purolator Classic. Why? Because it's an economical filter and I've had "good luck" with them.