It all depends on where you intend sailing, for how long your sailing excursions will be and how often you intend diving
. No use lugging 2 or 4 pre-filled bottles along if you are planning a 4 week diving
trip. If you intend visiting remote parts
of the world, you have to be fully prepared. We have a Bauer Mariner 320 (big compressor) on board, we love remote
islands, we dive often and we are very happy with our setup. We also often fill tanks
for other yachts on barter|trade deals and thus making it more cost effective.