It's personal preference. Some prefer rayon, some hemp, organic cotton, Japanese cotton, etc. I personally prefer Japanese cotton. Never tried rayon, nor hemp.
I have tried a lot of different cottons and I keep going back to Japanese, the thickness of different brands is the only difference I have noticed. All the other ones like vapers choice and native wicks seems to be the same, they almost seem to dense to me once wicked up.
I would stick with Japanese and wicking techniques makes all the difference in the world
I like Rayon best, but cotton works fine for me, too. I've noticed I have to change the cotton way more frequently, and it's not quite as flavorful as rayon. Just my experience.
I got mine from a PIF box about a year ago. 5 feet has lasted that long and I'm nowhere near out yet. Sally's Beauty Supply sells it online and in store. I have a link somewhere. Has to be a certain box #.