Forget about having to bleach and stain wood every other year. With the money you save by not using these coatings and cleaning materials, you can recoup the higher cost of composites in about five years.
Composites don't rot or attract termites, they can't warp or check, and you can go barefoot without fear of splinters.
All composites turn a slightly lighter shade after the first two or three months in the sun, then the fading stops. (Left to its own devices, wood inexorably turns gray.)
Up to 20 feet, which means fewer end joints.