Klepper claim their hulls are good for as long as 50 years with proper care, or roughly double what might be expected of a rubber coated hull. Some boats, like the Klepper Expedition models and all Feathercrafts, have additional strips of material glued to the hull to reinforce areas where abrasion would be highest. One major difference in boats is the type of cockpit. You might think that the open cockpit boats are easier to get in and out of, and generally that's true, but most paddlers use a spray deck on open-cockpit boats, and once you put a spray deck cover on an open cockpit boat there isn't much difference. Open-cockpit boats do have the advantage of being somewhat more flexible in use.
Sailing is easier in open boats, and drop-in rowing units can be used in most open doubles.
Some factors to consider in selecting a folding kayak. A list of recommended books and videos, including links for ordering. A number of folding kayak related web sites and mailing lists around the world. Accessories for Kayakers Safety equipment, navigation gear, storage and more. Watch for new additions.