Everyone will disagree with me, but if it is a choice between a DC and an
air filter, I would go with the airfilter.

A DC will do little for your tablesaw, miter saw, disk sander, or drill
press; and a shop vac will work for the router and jointer (though not as
well as a DC). But neither will substitute for an airfilter.

I think a DC only comes into its own on a planer; but you don't have one.