Rayon has a nice sheen, but is weaker than poly and isn't colorfast with bleach products. It has its uses, but you don't want to embroider something with it that will get lots of wear and washed a lot. I'm using up all my rayon now and only buying poly. I have towels embroidered with rayon that are fine, but for example, you don't want to put rayon on pockets of jeans etc. that will get rubbed frequently.