Nylon and Polyester are nearly identical in most ways. When it comes to the major specifications such as UV, abrasion and mold resistance and strength are effectively the same.
The main differences between Nylon and Polyester are the stretch and the ability to dye. Nylon rope stretches significantly more than Polyester at break. 100% Nylon rope (such as our Knotrite Nylon) is dyeable where Polyester will not readily accept dye.