Well, in terms of efficiency - at least that's what I thought.
In a direct conversion of electricity into heat, the efficiency is 100%. It can't be higher or lower (where else should the energy go if not into heat?).
To show a different approach... A wood-burning stove might possibly be another alternative. Heats up quickly and well. However, for your intended use with open fire, it is probably not an alternative.
Oh, now the high-tech followers are coming. Kaho, put the cheap oil foxes in there or buy one or two wall panel heaters from Siemens. They don't cost much either. What it costs, it costs.