Since you don't intend to carry a lot of gear, look at the design displacements of the boats that you are interested in. You don't want to find yourself feeling too loosely fitted in a large volume boat. At your weight, you may not sink a 17' Great Auk for optimum performance. Have you paddled 24" wide kayaks vs 21" wide kayaks, whether plastic or otherwise? Do you want to learn to roll, and be a true sea kayaker? A narrower kayak may prove just as stable for you, yet be easier to roll. A wider kayak may suit you better for photography and sightseeing. Paddle a few boats. Check out One Ocean Kayaks also.