This is largely a question of what material you feel most comfortable with. Someone with good woodworking skills would head towards a wooden boat while someone with fiberglass skills will see flaws in a glass hull as easily repairable. Steel and aluminum hulls require a more specialized skill but for those who can weld and work with metal that may be the way to go. Fiberglass hulls are the most common type found so that makes finding experts to undertake repairs that much easier. Fiberglass is relatively easy to patch whereas the other materials do require a little more expertise. Remember that fixing the hull is but a small part of the overall renovation. Pipework, electrics, and electronics together with pneumatics and hydraulic systems are all part of the renovator's to-do list.