Cost really is a non-issue in the choice.
Unless you use a ton of propane, the convenience of electric makes it worth paying an extra $5-10 per year with electricity.
If you use that much on a seasonal site, see about getting a propane company to bring out a big 100gal tank but unless you do a lot of winter camping, it's unlikely to be worth it.
Tammy & Mike
Ford F250 V10
2021 Gray Wolf
Gemini Catamaran 34'
Full Time spliting time between boat and RV