While both materials work really well for Barwa covers, there are a few reasons to go one way or the other. Barwas originally used a heavy cotton canvas, and we offer one that perfectly matches the specs of the original. That said, the acrylic fabric we use is fade resistant and will hold up much better with outdoor use. It is also offered in superior color options. Our advice is generally to go w/ acrylic for better aesthetics and functionality. Cotton has a slight edge on comfort and is a great option for an indoor chair in our opinion.