Lower power consumption for the same brightness, some have a combination hid and normal beam for high and low, some have a movable reflector that moves the light for high and low.
they last longer then a normal globe as they dont break filaments with vibrations.
going hid and led indicators will reduce the load on the altenator for the same amount of light.
but the arctic blue normal globes are good as well if you dont go the hid path.