A three piece (after it comes out of the mould, its cut in three pieces(adds to the cost price) & watertight bulkheads fitted, it allows you to airfreight your kayak for expeditions abroad!
A three piece kayak can be put in the back of an estate instead of on the roof of your car! Making it easier for transportation.
If you dont have the stength to lift a normal sea kayak, with a three piece you can put it together at the shoreline.
Composite construction means stiffness so that paddle forward motion is maximised
A plastic boat may deform or flex which means not all effort is used in forward motion