Worse than a heat pump, yes, but very arguable whether NG is more efficient. Arguably, NG powering central electric power generation and then used for resistive would be overall more efficient. Central NG will be more efficient and also there’s substantially less opportunity for NG leakage if piping was reduced.
NG is definitely cheaper (at least in the US), but that’s not really related to efficiency or emissions cost.
Also, if you’re in the electric ecosystem, swapping to heat pump systems will obviously be lower overall power in basically every scenario, and it gives an easy transition path unlike NG.
Maybe... I've got a NG furnace now and am looking at adding a heat pump, and even with a pretty expansive budget, I'm struggling to make the numbers work on actually removing the furnace entirely vs. doing heat pump + furnace. (And the near-impossibility of upgrading my home service past 100A makes it extra complicated if I want to electrify everything.)
If the evaluation is total lifetime cost to you, using the equipment you currently have almost always wins out. Same with purchasing more efficient hvac and such: the cheapest/lowest efficiency hvac is almost always the most cost effective. That tide could turn with sharp increases in NG or electric prices… but it hasn’t historically been true for many years.