Composite boats are bigger and lighter. (I’m looking at the 19’ Seaward Quest) Plastic boats seem more durable and easier
(I’m looking at the Prijon Kodiak.
Between those two boats, if you are not an experienced paddler, go for the Kodiak. More forgiving, while still large enough for a big guy and his gear.
Back to the larger question of plastic vs. composite, it is true that most long distance expeditions have been in composite boats (Jon Turk, however, has done some truly crazy routes in plastic boats, including a Kodiak), because composite tends to wear better for abrasion in the long run, as indicated above. While plastic fuzzes up and wears down, composite boats can be easily repaired for abrasion damage.
BUT if the question is impact, then plastic usually wins, which is why WW kayakers like plastic and canoers on bony arctic rivers have favoured ABS or its contemporary substitutes. Sea kayakers tend not to smash their boats onto rocks so much as they scrape them over reefs, barnacles, etc.
So, if I was planning a boat for one remote expedition only, and I wanted maximum durability, I would go for plastic. But if I was planning on paddling a boat over many trips and keeping it long term, I would go for composite.