I guess my thinking is way off as usual. I was thinking with more filtering surface I would get better suction. I guess not. My bag that came with the collector filters down to 2.5 microns and as I understand it the dust cake that lines the bag filters it more. I may be wrong about that to.
I think more filtering surface area is better. That's why they Wynn (and lots of filters) use pleats.
As far as dirty = "better filtering", that's correct. But the dirtier it is, the less suction of the overall system.
Wynn discusses this pretty well at this page:
https://wynnenv.com/filter-efficiency/
To cut to the chase, see their table here:
https://wynnenv.com/wp-content/uploads/NANO-522-Data.jpg?x35957
The row across the top is the "Delta P", which is the pressure drop across the filter. The bigger this value, the dirtier the filter, and the harder your DC motor has to work to pump the same air through the system (it generally doesn't work harder, so the airflow decreases). But notice the dirtier it is, the better the "Fractional Efficiency" (the percentage of particles blocked at the specified particle size)... that is, the filtering gets better. Cool stuff.
I would still get the Wynn, because you're going to have to clean any filter, at which point you're breathing what it's not catching. But that's my lungs & budget. Although so far I've survived prostate cancer (you really don't know you've survived until you die of something else), I don't want to try my luck at lung cancer.