Lighter, stronger, no risk of rot.
That is why se stop using plywood in that size range.

jacques, boats with balsa cored decks virtually ALL become squishy soft over
time. boats with plywood cored decks almost never do, and those that do, do so
only in small areas. plywood cored decks are almost as long-lived as solid
fiberglass decks, and weigh less.

Have heard repeatedly from highly experienced, long term naval architects that
plywood hulls covered inside/outside and between plywood sheets are stronger
pound for pound than most any other material out there. About the only thing
that beats ply is damned expensive composites.

Very few plywood boats out there, though. People think they are wood and
therefore won't build they from scratch and won't buy used ones.