All resistive electric heaters have the same efficiency, regardless of their shape, methodology, or what the manufacturer prints on the box. That efficiency is 100%, i.e. all of the electricity put into them gets turned into heat, one way or the other. The same amount of electricity (up to and including the locally specified legal maximum for a standalone appliance, which in the US is 1500 watts or roughly 12.5 amps) becomes the same amount of heat. It doesn’t matter if the manufacturer put “for large rooms” or “for small rooms” on the box, or what. 1500 watts is 1500 watts.

However in ideal conditions and specifically for the purposes of heating, a heat pump can achieve efficiency of over 100%. Which sounds impossible, but only until you realize that a heat pump’s method of operation is not to create heat but rather to move heat that’s already there from the outdoors to inside.