Electric. Electric vehicles are designed for indoor use only. Their big advantages are the absence of fumes and their quiet operation. If you only intend to use your vehicles indoors, this is the way to go. In multi-shift operations you will need additional batteries and charging/transfer stations. In single shift operations, or, if the truck is not used 100% of the time, you can charge it during off hours. Note that the batteries and chargers for lift trucks are usually priced separately from the lift truck itself.
LP Liquid Propane. Advantages of using LP include minimal fumes (however heavy use indoors requires adequate ventilation), the ability to use both indoors and outdoors, and the ability to quickly change LP tanks. Commonly used in indoor/outdoor operations such as lumber yards.
Gasoline or Diesel. Outdoor use only. Heavily used in construction, scrap yards, etc.