Here are a few insights which will help you choose the right one.
Muslin fabrics are made from 100% lightweight natural cotton. It is very soft , can be easily dyed for any application and is non-reflective.
Seamless paper rolls are versatile for almost any shooting space. Backdropsource offers up to 50 colors to choose from and are among the most cost-effective studio backdrop options available.
Here are some difference between Muslin & Paper
|Cotton Muslins||Paper Backdrops|