Space heaters

Wiki says that natural gas or propane heaters are cheaper to operate than electric ones. Speaking from experience and knowing how expensive propane is, I’ve found it’s cheaper to heat my house (normally 65º in the winter) with the propane heater and one of those oil-filled space heaters.

I like the oil-filled radiator-style electric heaters. One will make my bedroom (the largest) comfortable, the middle-sized bedroom warmer than I like, and the little bedroom quite toasty. A friend says she’s heard that ceramic heaters are more efficient. I couldn’t disagree, since I don’t know. I do know that once the oil in the radiator style is heated it will stay warm a long time, and I assume it takes less energy to maintain the temperature than it did to heat it in the first place.

So which is more efficient (i.e., cheaper to operate): the radiator style, or a ceramic one?