I have both and they are as big as I can get them . Presumed listed all the obvious advantages of silk. Cotton will absorb more water should you need to gather morning dew etc. I've used mine for just about everything, including a wet clay poultice for a nail puncture in a mule's hoof. They also make nice signal flags, so get something bright for at least one. There are lots of makers. A websearch of western tack should find many. Silk tends to be expensive. The edges should be rolled and fully stitched.