Regardless of what manufacturer's marketing might imply, there is no real electrical efficiency advantage between types of space heaters, i.e. coil, ceramic/infrared, oil-filled radiator, etc. Electrical conversion of watts to BTUs is pretty much a constant, and one might choose a particular type based on other criteria such as zone or room heating, or as previously mentioned, features such as safety, ease of use, timers, quietness, size or looks.
Efficency is gained when heating a small area versus an entire room, or heating a room versus a floor. Infrared heaters are more directional and therefore are more "efficient" when directing heat to a specific area such as when sitting, versus trying to circulate heated air for comfort anywhere in a room.
Steve