Oil-filled radiators work by heating oil stored inside the heater's body. Micathermic panel heaters heat thin sheets of mica, a kind of stone. Micathermic panel heaters produce heat more quickly but oil-filled radiators retain heat longer.
Micathermic panel heaters are much lighter weight than oil-filled radiators, so it's easier to move them from room to room. They're also flatter, so they fit into tight spaces more easily.
The U.S. Department of Energy recommends oil-filled radiators because they store heat more effectively. As a result, this type of heater is more energy-efficient than a micathermic panel heater.
All space heaters can cause burns. Some micathermic panel heaters lack a safety mechanism to turn them off if knocked over. Oil-filled radiators can leak hot, flammable oil, creating a fire hazard.