Where I am I have no choice but to use propane, so it's a moot point. However, NG provides just over 1m btu's per cu. ft for approx. $.01 and propane around 2500 btu at around $.03 cents. Prices vary a lot by time of year
and region of country. Both sort of track up and down with crude prices. NG is lot cleaner burning than propane.
Propane pricing is not controlled. Propane cos like to lease you a tank, you are then a captive customer and they bind you to a contract or price gouge you. We made the mistake of leasing a tank when we first moved rural, but quickly learned the game, purchased our own tank, convinced the neighbors to do likewise and now collectively bargain for the best rates. We actually get better rates by having an independent Eugene distributor (who is 60 miles away) supply us than large companies in our own town. And I'm talking dollars per gallon cost differential, not pennies. We were mad as hell when we first discovered this.