I tried using K&N filters from before many of you were born. Part of being a teenage motorhead is aftermarket is better. One of the tests discussed maybe 40 years ago was putting some white lithium grease downstream of the filter and using it as a guide for a contamination check. Of course, that's harder today not to contaminate the MAP. But as hard as I could, it usually showed more contamination than the stock filters. Sometimes they were a better filter to use when running enduro bikes in the Pines, running through deep water streams.
It's always about the perfect amount of oiling, and that's why I said it requires a Master Class to be absolute.
Within my SEMA and SAE activity, I once had a discussion with an engineer from a filter manufacturer. He said many people reduce the filter's ability by blowing through it to clean it out, opening the pores. He also said changing it early hurts filtration. As the filter collects dust, the filtration becomes more restrictive, but also more restrictive to small particles. The best filtration is in the second half of the filter's life. The tough call is when is that restriction restrictive too much.
There can be, and are, better filtration out there. The tough thing is getting a solid, unbiased answer. Even test engineers are biased.