Heat Pump vs. Propane Furnace

My sister and brother in-law are in the process of getting bids on a new install. The home is a 2,200sf single story ranch style house in Southern California, so we have very mild winters. The home does not have natural gas and the current system is a propane furnace. Although they are soliciting a couple more estimates, we have a contractor who has done multiple installs for myself, friends and extended family who has done a great job both sizing and installing systems at each of our homes (zero problems). They are debating installing a Trane system either XV18 or the XV19 with the side discharge heat pump and TAM9 air handler or a system with a propane furnace. Energy pricing is a concern with no immediate plans for solar, but discussion of future install emerging and obviously possibly a swinging vote. Another concern for them as well as the installer is the area we live in requires the use of ultra low nox furnaces. He doesn’t seem to be a huge fan.

Current average pricing is:
$.47 kWh
$3.30 per gallon for lg and rising

A few questions: (Competent professional install given)

What would you want installed in your own home, and why?

How would I compare the usage costs between an 80% afue and the aforementioned heat pumps? Per unit pricing is easy enough, but how do I account for the added efficiency above 100% that these heat pump models provide?

Is the XV19 with the potentially higher SEER and HSPF #’s worth a marginally higher cost?

Thanks,
Garrison

source https://hvac-talk.com/vbb/threads/2240547-Heat-Pump-vs-Propane-Furnace?goto=newpost