Though often grouped with composite decking, vinyl decking is really in a different category. It is all plastic and not a composite of anything. It tends to be more expensive, and it promotes certain advantages. The primary advantage over composite decking is that it contains no wood content. Wood in any form, whether whole or ground up, is fibrous and can absorb moisture. The composite decking companies are, of course, aware of this and deal with it either by capping the composite with vinyl or HDPE plastic or by making the composite mixture less absorbent. Vinyl decking is absolutely impervious to water or moisture. You will see the term "waterproof" appear frequently on vinyl decking web sites.
There are a number of companies that make vinyl decking. The most established and best known is Azek®. Azek has now merged with TimberTech®, and their web site can be more than a little confusing because TimberTech was a composite product. Like most of the decking web sites, the TimberTech web site promotes it products in different style sub-brands. The TimberTech Azek Vintage, Arbor, and Harvest "collections" are all described as "capped" but also "100% PVC (both in the core and surface)". It appears that a different PVC formulation for the capping provides an better level of scratch and stain resistance. It should be noted that not all plastic is the same. And not all PVC (poly vinyl chloride) also called simply "vinyl" is the same. Each company employs experienced chemists who develop unique formulas. Read what Wikipedia has to say about PVC, and it will probably make your brain hurt if you're not a chemist. Formulas can make the material more flexible or more rigid… just as an example. The point is that there are hundreds or perhaps thousands of variables in how the PVC is made.
Other companies that produce PVC decking are Tufdek®, LB Plastics, Fiberon, Genovations, and others. Fiberon is a well known maker of composite decking, but they also have an all-PVC brand.
Tufdek has put a lot of development into making its decking look like real wood with both texturing and coloring.
Above: A photo from the Tufdek web site showing their new rustic style. The photo at least absolutely looks like wood, not plastic.
Above: A photo from the LB Plastics web site. Most vinyl decking is solid. This product looks like a structural solution that is both strong and light weight.
Genovations also makes a structural format that is not solid. The web site points out some real advantages.
The point of this article is that if you are planning a new deck, you have a lot of options. The good news is that very smart people all across the country have put their minds to coming up with new ideas and designs for decking. The result is an array of really great alternatives to wood. It will be worth two or three evenings of your time to check out the web sites these companies have built. They tend to focus on color and style choices with adman names like "harvest collection," but there is also a lot information about how your deck can be built to both last and look great.