What I can add is if you ever want to use that spa in cooler temps you are going to need the gas. No way a spa will heat up for you if it's 50 degrees outside. Many people don't think about that. Also if you decide you want to swim in the cooler months you won't get much heat from a HP.
As for propane, if you own the tank you can get a better price on gas. If you lease the tank, then you are stuck buying it from the same company and at whatever price they feel like charging you.
As for propane, if you own the tank you can get a better price on gas. If you lease the tank, then you are stuck buying it from the same company and at whatever price they feel like charging you.