Sales personnel will tout the warranties of carpets. But all warranties are conditional and therefore virtually useless in my view. This is not a scam. It is true that carpets must be maintained properly, and that poor maintenance legitimately invalidates a warranty. Consumers must find the best compromise between durability, stain resistance, appearance, and cost.
Nylon is generally the most durable and resilient, but is the least stain resistant.
Polyester and olefin are less resilient than nylon, but are more stain resistant. Selecting a carpet is difficult because carpets can be infinitely varied depending on the mix of fibers and textures. The best advice on selection is to simply closely study carpets. Look closely at the individual piles. Study the most and least expensive carpets.