Most sport rappellers start out with a Figure Eight. However, Figure eights aren't always the best option as they put large bends in the rope
,decreasing the life of your rope
more quickly than most other descenders.
Cavers tend to use Racks and Bobbin style descending device.
Climbers prefer using their belay device
to descend as it avoid having even more gear and most tube style belay devices
do not twist the rope.Full Article