There are many factors to consider when selecting composite decking. Not all composite decks are made the same. Some newer composite deck materials contain recycled materials. Not all composite decking have the same density and strength. There are many manufacturers of composite deck boards and composite deck railing.
Composite decks would seem to offer the best of both worlds: wood mixed with plastic to create a product that looks like wood, but has added resiliency and longevity. However, since the woods used in composite decks are generally recycled woods that are not used for deck building in the first place, they tend to absorb water and can produce mold as a result. Composite materials are more expensive than wood but comparable with vinyl.
After five years you may need to replace your deck, as you cannot re-sand or refinish it like you can with a wood deck. Lastly, though you may not need to stain your composite deck every few years, there are still detailed cleaning instructions required to keep it looking good for the duration of its life.