100% poly is preferred by most for 1A style yoyoing (long spinning, string tricks). 50% poly/50% cotton used to be popular and some still like it. 100% cotton is the best choice for yoyos with wooden axels (other strings can melt from friction on the wood axel). Nylon mixes tend to feel rougher compared to most 100% poly strings.
kitty nylons last long and whip great. if theres training wheels for bikeing, theres nylon string for whips and slacks! andre recommended em for me personally ;D
I’ve been using 100 % poly exclusively for the last 3 years. I find that 50/50 feels a bit better between your fingers, but it just sucks up moisture when you’re outside.