Poly also hold onto oil like a magnet, and I call that not resisting stains. Poly, Olefin, Triexta are all crap. Nylon is king.I explain it to them simply. There are two main types of fiber in residential households, polyester and nylon.
The trade off is, polyester is like your credit card, it will bend and break physically but resists stains more easily.
Nylon is like a spring, it moves up and down so you won't get wear and tear but it can stain more easily if protectant is not applied to it.
Beyond that all I tell them is a high face weight of 80+ ounces is ideal for a long lasting carpet and to make sure they don't use an aggressive vacuum
I do try to educate the customer a little on fiber types only if I see a real problem in the home that already exists. Here's an example. I got a job about a month ago in a very high end home. The owner has not one, but two Great Danes. They also had 3 wool area rugs worth thousands of dollars with some high end carpets only in bedrooms and most of the home had hard floors. NONE of the carpets were damaged by dog urine and I was able to treat all successfully and cleaned up extremely well. All 3 of the wool rugs I believe are permanently stain damaged with possibly one that could be saved at GREAT COST. (I'd say perhaps 1/2 or more of that rugs retail value "might" save it.) The other two are permanently stain damaged to the extent I doubt anyone on earth can save them. I NEVER recommend regular nylon and especially natural rugs or carpet like wool to pet owners, period. Btw, the same customer had a polypropylene rug that I had zero problem cleaning and no stain damage.
I do recommend polypropylene or solution dyed nylons or polyester in either rugs or carpets if you have pets that almost always go in the home. It depends on what I think the customer can afford or is willing to pay. Wear, furniture dents, and over all durability are also things I discuss fairly regularly. Many polys are a nightmare for these issues and are basically crap carpets that are not very durable and do terrible with furniture dent issues in many cases. I want the customer to know why there's an issue and what to expect if they buy these carpets or rugs.