GAS....... They never need them expensive batteries and them little gas motors will last an enternity due to the low rpms they turn.
Change the oil once a year and keep the air filter cleaned and your good to go.
I have a Yamaha gas burner I bought from my dad couple years ago.
It's well over 20 years old and still runs perfect, it doesnt use a drop of oil and will seemingly run forever on a tank of gas.
I cant imagine how many sets of batteries a electric cart would of gone thru in 20 plus years.
JMO>Cp