What's better: Ceramic space heater or oil filled radiator heater?
Electric heating is 100% efficient so no differences there.
Technically they are both convection heaters however the oil filled radiator has a much lower watt density over given surface area and would be safer as no parts get to ignition temperature. The ceramic will produce a stream of warm air almost immediately so it's good for quick spot heating.
The radiator will take a while to chase the chill out of the room.