There are a lot of things to consider. I am usually a handquilter. For that I like the Bamboo or the lighter cottons. If I am making something for someone who will launder it a great deal poly is the only way to go. I make about 20 Linus quilts a month and for them I use the 4 oz. poly batting that comes on a ten yard roll from Joanns. Who has any idea how those quilts will be laundered so poly is the best way to go with them.
In the long run it comes down to what you can afford, how it will be laundered and how you like the look of the finished product.