Firstly your respiratory system is for breathing not filtering therefore workshop air quality is of the utmost importance.
I have a Jet AFS 500 which runs as soon as I enter my workshop, this filters down to 1 micron for a large percentage of dust. In addition, I wear a Trend Airshield (have just upgraded to the Air Shield Pro) and use a CamVac when sanding.
I find the filter screen on the AFS 500 needs regular vacuuming so it is obviously catching a lot of the airborne particles and continues running for an hour after I leave the workshop.
I can’t comment on other systems but am happy with what I have at present.
Dave