the material choice is based on your environment and proposed uses. Of much more importance is the type of paint or dye you want to use and that choice is made based on the keyer you prefer and your camera's capabilities.
Any good commercial green screen material will work just fine. In the expensive old days, the color of the green or blue screen paint or fabric was very critical, but with today's keyers you can key just about any solid color on any material if it is relatively well lit.
I prefer this product from Film Tools because you can stretch out any wrinkles very easily if mounted to a butterfly or frame, but I have used plain fleece fabric and other solid colors from our local fabric store many times and it also works well.