The many benefits of nylon make it the best choice for the multifamily housing market

Stronger and more resilient than any other synthetic carpet fiber
Exceptional life-cycle investment advantage
Only carpet fiber that can be repeatedly recycled back into carpet
Most commonly used fiber for carpet

Most nylon products are treated with a soil and stain resistance system.  Due to technical limitations, PTT cannot be treated for stain and soil resistance.  A significant advantage the treatment offers is repellency: Spills bead up on the surface longer, preventing moisture from soaking into the carpet backing and padding.   Both PTT and unscoured polyester are prone to soiling, and the soil-resist component of the combined stain/soil resistance treatment gives nylon another advantage.