Function
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.
Portability
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.
Energy Use
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.
Safety
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.