Commonly, underground tanks are safer than above-ground tanks. One reason is that it’s easier for these tanks to stay temperate in extreme weather, especially in the freezing cold. Underground tanks are also safer in the event of a leak. Above-ground propane tanks are less expensive. This is because you’ll only be paying for the tank itself, which fluctuates depending on the size of the tank and if there need to be any ground work that needs to be done.