When buying a satin pillowcase, it is important whether or not the fabric is silk?
Silk is the best option because it doesn't pull moisture from the hair. Other materials will preserve hairstyles, but can dry out your hair.
I think it's the satin finish that's the most important consideration.
silk is the best option because it keeps your hairstyles fresh and the other fabrics dry styles out fast while the silk preserves them which is important when trying to preserve moisture