For me, the decision between going plastic or fibreglass depends on where you intend to use it. If its gonna be for surf launches then you're going to have to go for the locally made fibreglass skis (Stealth, Tomski, etc). All good skis no doubt. Reason being is they are designed for that with their rounder noses. The plastics are ideal for here in the Cape where you can drag them off the rocks and launch anywhere you see birds feeding and fish tucking in. Watched 2 guys with plastics pop in their boats off the rocks at Millers last Sun. No need to use slipways and the like. Plastics tend to have sharper noses and faster to row, but dont do well in surf.
Hope this helps.