Most experts recommend carbon fiber heating elements over ceramic one. This is because of a variety of reasons. First off, carbon fiber heating elements are generally more efficient to run than ceramic.
They are also better at spreading out the heat, which will get rid of any cold spots you might experience in the sauna. This better heat distribution will also allow you to be in the sauna for longer since you won’t need as much heat to keep it running. Finally, carbon fiber elements are more durable than ceramic elements.