No gears to jam or break. No swimmers needed to position, feather, and lock or remove weeds from the propeller. No shaft lock needed. No unfeathering during a race or cruise. It offers an alternative propultion for heavier displacement sailboats, particularly hulls with a modified fin or full keel.
Larger gears provide reliability and strength.
ALSO, instant lubrication through a zerk fitting. Sweptback blade axes to shed weed, kelp, and lobster pots. All at a lower price.