Should I get a DE filter or a cartridge filter for my pool?

It depends on how much you hate cleaning. DE filters give you sparkly water down to 2-5 microns but require backwashing and adding fresh DE, plus disposal hassles. Cartridge filters catch down to 10-15 microns, are still plenty clean, and need only a yearly hose-off and replacement every year or two. If you want the clearest water and don’t mind maintenance, go DE; if you want less work, get a cartridge.