Re: direct drive
V-Drives often make it hard to service the engine as the service points - waterpump, alternator, etc - are hard to reach/
Saildrives are basically like the lower drive unit of an outboard coupled to an engine mounted inside the boat. Lots of aluminum in the water and if strict maintenance is not adhered to there can be serious corrosion problems. Easy for the builder though.
Conventional shaft drive like the diagram above is the simplest most reliable system.
Living aboard in Victoria Harbour