Nylon is the most elastic of all the fibers, so it is ideal for docking and anchor lines. Polyester has little elasticity but excellent weathering properties, so it is often used for running rigging lines. Spectra is very strong, extremely lightweight, has a low melting point, and will not absorb water, so it is suitable for running rigging for light loads. Polypropylene is also lightweight, has no stretch and floats, but it is very susceptible to UV light and melts under heat and friction. Vectran is very strong, does not stretch, and repels water, so it most often used on competition sailboats.
Plastics improve performance.
Boats go faster using these materials. Bob Defilippo, Hunter Marine.