It's rayon all the way for me, I've tried organic cotton, Japanese cotton, cotton straight from the field, silica, even some fluval I had left over from my old carto days and to me, rayon impacts flavor the least and wicks up juice the best. It doesn't work as well on the thin juices, but thicker juices are the kick. I typically go either 70/30 vg to pg or straight vg and rayon hasn't failed me yet.