Fleece or paper vacuum bags — which should I buy?

Fleece, in almost every case: it filters across its whole surface and holds several times more before the suction drops.

A paper bag blocks at its inlet face, so airflow falls long before the bag is full. Fleece is more expensive per bag and usually cheaper per liter of debris collected.

On fine, heavy material — ash, plaster, sand — the difference is a whole session against ten minutes.

Whichever you buy, order by the manufacturer’s bag code rather than the machine’s family name: the same range has taken several bag sizes over the years, and the collar that seals the bag to the inlet is what varies most between third-party equivalents.