Depends on how far apart the quilting is going to be because some you have to do closer and some have a scrim so you can quilt far apart, so it depends on your design and how you want the finished product to look. Poly comes out fluffier than cotton, but if you don't want bearding you need to get a high quality one because it beards( loose fibers show through the quilt top) more than cotton. Warm and natural are fave among many. Hobbs 80/20 poly cotton blend are another fave. quilters dream is also quite popular. Also the warmth is also a factor to consider. Cotton breathes better than poly. Wool batting can be nice as well