I get asked by customers, what would you recommend we get for new carpeting? My favorite is wool and nylon low pile or berber type carpet. But, not everyone loves low pile or berber, and not everyone can afford wool. So, if you had to get one fiber that meets affordability and longevity, I would say whatever you choose, get nylon at least. There has been numerous occasions, I am asked to clean 1 year old polyester, where the traffic lanes have been permanently damaged due to shoe wearers. Even though polyester is less expensive, and more stain resistant, it is very soft and wears fast. If you need inexpensive carpet for a rental or need to make your home look good for a sale, then yes, jump on that band wagon and get polyester. But, keep in mind that you will be replacing that polyester in your rental sooner than you expected, unless you have a “no shoe” policy on your rental agreement.
Nylon is a great fiber, and can last a long time if you regularly vacuum and steam clean. Small dirt particles is the main enemy of all fibers, so it is importa