All carpet mills make different grades of carpet. When you figure price and quality, nylon is your best buy. Never buy because of wear warranty, nylon doesn't wear. It uglies like all carpet. Wool is a better fiber, but too expensive to allow the cats to get sick on. Polyester is cheaper, but will mat worse than nylon.
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Installing since 1973
i own a carpet cleaning business and have a few thoughts
1. you do not want wool, it's harder for us to clean and relies on the treatment for stain resistance. if you're really clean with no pets this is great carpet
2. quality nylon with a good factory stain resistance treatment is golden with animals. when you do have your carpet cleaned the prespray should be a ph under 10. the really aggressive pre sprays will kill the protector. also, every year or two having the cleaner re apply protector will make stains MUCH harder to set in the carpet.