On a basic level, Battleships are the new-player friendliest class.
Cruisers can be out-detected and die quickly from armor that works in skilled hands but eats damage in non-skilled hands.
Destroyers have low health pools and are quickly killed when detected if helm'd by a new player
Carriers are a class which has a subset of the base audience due to their different playstyle/mechanics
Battleships have enough armor to not die easily, and big enough guns to hurt what they shoot at. It's a great class for a person who doesn't want to load into a game and shortly after be sent right back to port.