There are exceptions to everything I am saying below, but, these statements are good generalities.
A brief overview of smoker types by heat and smoke source:
** Wood burner, such as offset smoker. Burning wood provides heat and smoke, typically the fire requires regular tending.
** Pellet burners, such as traeger. Burns wood pellets to provide heat and smoke, typically automatic control of heat, most expensive fuel.
** Gas burners, burns propane for heat and uses wood pellets or chips to provide smoke. Usually not thermostatically controlled.
** Electric smokers, uses an electrical heating element for heat, burns pellets or chips to provide smoke. Usually thermostatically controlled.
** Charcoal smokers, such as weber smokey mountain. Uses burning charcoal for heat and uses wood chunks/chips for smoke. The better units are stable with less fuss than a wood burner.
Some people find tending a firebox fun, and part of the experience. Others find it frustrating and tedious.
Pellet burners have some of the highest operating cost, due to the price and quantity of pellets burned for long smokes.
Gas and Electric smokers must use pellets or wood chips to provide the actual smoke needed. As these units come from the factory, the wood chips and pellets need to be replenished every hour or so. This is less effort than a wood burner, but it ties you to the smoker for long smokes. There are modification the end user can make to provide smoke for the duration of the burn at extra cost. High end charcoal smokers can be almost as fuss free as an electric or gas smoker, which has been modified for a longer smoke supply. Charcoal burners can also have a "stoker" added to them for automatic temperature regulation, making them hands-free for hours at a time.