My opinion: +1 on Deb's "cartridge filter" and Cassandra's "separator", for different reasons.
For the filter, check the bag on top's filter rating. Bag filters can run 10 to 30 micron or more while cartridge filters today are often rated to 1-2 microns. The more of those fines you *don't* breathe, the better!
I have a Jet and plan to add a separator (probably a 30 gallon wastebasket-type) in front of its suction. When I use the jointer or especially the planer, I can watch it fill. For me, at least, it's a nuisance thing. I've emptied my bag on a Friday afternoon and had it half-full by Sunday evening.
Your mileage may vary... :-)
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