We often camp with electric hookup, and when we are paying for hookup I don't want to use propane I have paid for separately. Hence we use an electric heater.
We tried small fan heaters, but they weren't silent. There also seemed to be something of a arms race for increased wattage, which is not ideal when many campgrounds we stay in have quite limited amperage available before the supply trips out. Plus we aren't heating a domestic sized room, so don't need big wattage.
As mentioned above those oil-filled heaters can be quite large. I've also noticed they can make popping noises as they heat up. And because they have a mass of oil to heat the heat supply isn't instant.
I settled on a small cheap heater I attached under the dinette. It simply has a heating element within it and uses convection rather than a fan. I think it was designed for heating greenhouses. Small silent and has a thermostat.
Steve.