It is generally available much earlier as, unlike its counterpart, it does not require Steam Engine to be researched before it can be built. The Naval Hospital is an alternative to the Steam Drydock.
From the navy's point of view, their men are returned to duty quickly and cannot desert or be "crimped" (pressed into service) by unscrupulous carers. The navy pays for doctors and surgeons to cure his infirmities: he has a bed in a clean ward, and best of all, he cannot spend his pay on drink and loose living. A sailor who finds himself looked after here can count himself lucky! A naval hospital gives high-quality care to the sick and wounded.