The steel hull would depend on how it was built. Ideally the framing will be flat bar so there are no spots where water can collect below. A lot of steel boats are foam insulated and there is no easy way to inspect the steel under the foam. Steel boat hulls rust from the inside. Of course there is the ongoing rust problems on deck but you can see those to deal with them. Any boat can be destroyed if you hit a rock hard enough. Fibreglass will have a lot less maintenance long term.