I am a former carpet sales person and interior designer. Let me tell you, polyester carpet is the best in my opinion. But you must compare apples with apples, and oranges with oranges. You cannot compare a loosely twisted poly with a tightly twisted nylon, or visa versa. You must compare loose with loose and tight with tight. Also, you cannot compare a dense carpet with a thin carpet. Once you have those specs the same, then compare. You will find the poly carpet is virtually stain resistant. If you can't get a coffee stain out, you can use bleach, and it will never fade under a window. Whereas a nylon carpet will be an irreversible mess in both cases. The Scotchguard, Dupont, and other treatments run the commercials, and therefore run the carpet industry. Wise up, because they wear off nylon carpet in time. Nothing wears off poly, because the intrinsic nature of the material resists staining without a top coat. It is far cheaper to make, if you stay away from all those topcoat names, therefore you get much more for your money and can afford denser and tighter. Hope that helps.