I think our misunderstanding comes from different meanings of the word efficient (or applying it in different contexts). I think the more accurate word you're looking for economical. Heat pumps for heating may be 5x more economical (use less energy overall, but they aren't as efficient with it), but resistance heating is 100% efficient (if we look at the efficiency after the electricity has left the socket, all that energy turns into heat inside your house; 100% efficient.)

And while heat pumps are transferring energy, there is loss due to inefficiencies. If you're trying to transfer heat from inside to outside, especially when outside is hotter than inside (like in almost every AC scenario), you need to spend energy to compress a refrigerant, cool it, move it inside (meanwhile it's gaining heat during the entire transfer process) and then use it. Also, components like the compressor and radiator fan aren't 100% efficient, and will be giving off heat.