Nylon curls super easy. It holds curls a long time. Its what MLP has.
Saran does not curl well, and does not hold curls well. It has a slightly greasy feel to it at times. It works best or straight hairstyles. A lot of MH dolls have saran or kankelon.
I just finished my first reroot, and i used nylon. Im very happy with it and i feel it gives me more styling options.