In beginner boats, wider means more stable. Deep V hull shapes and round hulls feel tippy, but as you develop balance and skills these hull shapes become preferable for intermediate and advanced paddlers. Wide, flat-bottomed hulls offer a great feeling of initial stability, but tend to slam in rough conditions. Fiberglass and Kevlar boats are lighter and faster but not as durable as plastic in the long term. Exercise care loading and unloading them and avoid scraping boats against rocks when paddling and landing.
Plastic boats are heavier and also tend to scratch.
As with whitewater kayaks, plastic is divided into crosslinked and linear polyethylene, both used in rotomolding. Wood sea kayaks are beautiful creations, much like owning a vintage automobile. They are either strip-built or made of plywood, and may be covered with fiberglass or epoxy. Folding boats are highly specialized and many are state of the art. Frames are made with wood, plastics or metal, and are either shock-corded like a tent or feature delicate fittings.