I'm not an expert, by dry air has a very low heat capacity. So you get a house with cold walls, floor and roof. And the dry warm air is rather ineffective in transferring heat to the walls, floors, etc.

In contrast, if you have underfloor heating, you have a relatively large surface filled with warm water that heats up the floor. And then you have an even bigger surface that transfers heat to the rest of the house.

In the end the house is more easy to heat because it doesn't depend on an airflow to reach all parts the house.

Heat pumps move heat they don't make it.

Air source heat pumps are at least 300% to 400% more efficient than just electrical resistance heat. Ground-source heat pumps are even more efficient.

All you do is use a bit of electricity to power a pump and some fluid to move heat around no need to burn things. Even better if the power comes from solar, wind, hydro, nuclear.