There is some merit in steel if you are planning to go to areas where there is a good chance of hitting hard things - rocks, coral etc and you want to be able to withstand that better and repair easily. However, most people do not want to do that, and as already said the risks of hitting something at sea are almost non existent - and anyway many of the few examples that have did not sink straight away.
GRP is far and away the best material. It gives you the widest choice of designs, is relatively easy to repair, is durable and will tolerate neglect far better than anything else. Steel does have advantages (as does Ferro) if you are building yourself, although this is nowhere near as popular as it once was - partly because of the availability of perfectly adequate GRP boats at a fraction of the cost of building from scratch (never mind the several years work).
Professionally built steel boats can be attractive, but they are extremely expensive - prrtly because owners stick things like teak decks on them to make them more attractive visually. Lovely when new, but have a look at 20 or 30 year old boats and see the troubles in store for future owners. Utilitarian steel boats can be successful, but you have to accept that few people like them, so values are low in relation to building costs. Again look at older boats that can be bought for very little money relative to GRP boats of similar size and capability.
The "safety" bit is over exaggerated. Cruising, even in the more remote parts of the world is a very safe activity. Boats, gear, communications, sources of help etc are now such that much of the "risk" from the early days has gone away.
Composite hull, with kevlar reinforced bow above and below water line for impact protection, carbon cross beams for rigidity and strength in widest sections, stepped keel to hull joint to transfer grounding loads into hull rather than pushing rear of keel up into hull. That was my choice, a Bavaria.
However I do like the idea of Al, despite the electrloysis issues.
quicKutter rope cutter, shaft and rudder bearings
If you look at boats that are 30 years old however there is no question. Solid fibreglass lasts much better and is not harmed by long term neglect. So the ownership thing beyond just safety in crossing oceans points to f/g as best. olewill
I don't think there is a right answer here.
if you want a metal boat then Aluminum has to be high on the list.
But a strong GRP boat is a great all rounder.
Concrete and steel (Ferro) is pretty tough too!
John Rodriguez Yachts. Cruising & Bluewater Yachts www.jryachts.com
The answer to the question is there is no answer, Iīm afraid. Anyone who says "X is the best material for a blue water hull" is talking b*llox. A blue water boat is just one huge mass of compromises as it has to be so many different things at the same time. Your call at the end of the day, everyone has an opinion.
I went for steel which has many benifits and many down sides. If you keep on top of the maintenance itīs not too bad, let it slip a bit and you pay the price.
The offshore safety bit is hard to answer, not enough data really to get a handle on. A more important question might be "How much am I going to worry about hitting something every day for weeks on a long passage?"
I asked around before buying about sister boats to the one I got, in one season 4 boats hit whales coming back across the Atlantic, 2 sank, 1 limped into Bermuda and the steel one really p!ssed off the whale without a scratch
I worry about many things offshore and getting holed is there, just not at the top of the list.
Steel because firstly it can stand deformation that is it can get dented and secondly if you carry a small oxyacetylene portapack gas welding set up ;a a few bits of suitable plate angle etc plus an angle grinder; you can stick it back together anywhere anytime-even in the water!