The question isn't about efficiency, it is about the unit's heating capabilities and required load. And your question is also not about HP vs DF, but HP alone or HP with Gas Aux since that is what DF is in the first place.

I'm happy with my HP, but I also have a wood insert for colder days.

Depends on home, insulation qualities, electric rate vs nat gas rates, and location climate.

The low cost of nat gas at this moment coupled with ever advancing electric rates have made DF and straight HP with air handler less advantageous.of course, many in the South have no choice if in an all electric situation.

Make no mistake though, today's modern HPs do a good job in both heating and cooling.

IMO

If your home is drafty and badly insulated, you will typically need more heat, and discover the heatpump running alot to maintain the temperature. In a situation like this it won't be as comfy and probably better served with heating with natural gas unless its very mild outside (say above 40).

If your home has efficient windows, attic insulation, and no major draft leaks in doors, the heatpump should keep the home pretty comfy inside down to a colder temp.

My home is older (late 1960's), without wall insulation, but its brick, has great attic insulation, good replacement windows, and sealed some leaks. I find the house is pretty comfy with heatpump heat down to about 25 fahrenheit outdoor temperature.

The SE is a pretty big area. In my area, most have NG alone. But get a little warmer, it changes to HP. DF is for areas with low electric rates which I have.

Of course, most of the SE has low electric rates so either DF or HP are good choices.