While plastic (typically polyethylene) surfskis are considerably heavier than their fiber based (fiberglass, carbon, Kevlar) siblings, they do have a very significant advantage over their lighter counterparts in terms of durability and capacity to absorb collisions and abrasions. If you are anticipating rough care and/or negligent storage habits for a surfski OR you want to use a surfski for rivers or shore breaks where bumps and scrapes are likely, then a plastic surfski might very well be a worthwhile investment. They are also less expensive than their fiber construction equivalents.
Many of these models are no longer being manufactured, but due to their durability they can still come up for sale (used) from time to time. Or if you advertise that you are looking for one, you may spark some owner's recollection of the one sitting in their back yard that they no longer ever paddle. But pay attention to UV damage/sag if the boat has been basking in the sun for a long time. Sag can sometimes be corrected by flipping the boat for a period in the sun. Ultimately these boats should probably be stored sideways?