Anything with a little cotton in it will shrink a bit - but a good cotton/poly mix is my favorite for batting. When "they" say shrink...it's not so much like when you buy a cotton tshirt and it shrinks two sizes smaller. LOL If you've ever seen pretty quilts that have been washed and dried a dozen times and how they are crinkly and antique looking...that is what cotton does. It also has a distinct drape...and cotton poly has it's own distinct drape, a nice benefit from the cotton in it. I think batting is completely personal preference, but I really haven't found one I would turn my nose up at!
