What is the difference?

This might soung stupid, but what is the difference between “slick” 50/50 string, and 100% poly strings. To me, they play almost the same, so what’s the difference?

Slick is half cotton half polyester. 100% polyester is just that.

slick wears out faster and is a little more responsive than 100 poly, but because its half cotton, its good to use on fixed axle yoyos. You shouldn’t use poly string on fixed axles because the friction makes heat which melts the the poly and breaks the string. i know from experience.