Thanks all for the recommendations.
Working at an OEM is frustrating because I have the full engineering data for the cars I engineer so it's frustrating to buy stuff for the cars I actually own because the detailed data I am used to is simply not available.
As an example here, I want to know the filtration efficiency of a filter (x micron at x % efficiency). I can tell you that for a high performance modern engine with a high demand oil flow, this would be something like:
95% 25micron
75% 18micron
50% 14micron
The WIX 51069 filter only specifies a 'nominal micron' value of 21. This means it filters 21micron at at least 50%. A bit ambiguous. However they also very handily specify the Beta ratio expressed as 2/20 = 6/20. Basically this means that it has 50% efficiency at 6microns and 95% efficiency at 20microns.
This type of filter leans a bit more towards filtration over flowrate.
I couldn't find the info for K&N, but I would guess they lean more towards flowrate and as such their filtration efficiency is probably a little lower.