I use a high loft poly batting. I have found very good quality at Walmart or Hobby Lobby.
My favorite id the Warm and Natural. I use any kind of cheap batting for my small projects like wall hangings, etc. THings that aren't going to be washed much.
It sort of depends on the quilt I am making and the effect I want. Quilters Dream brand is my number 1 favorite. Followed by Warm and Natural (machine quilting only) For hand quilting, I love wool and also Hobbs. The one and only thing I will buy at Joanns is batting with a 40% off coupon. Also Hancocks in Paducah has pretty good prices. Google "compare quilt batting" there are lots of good reviews/pros/cons of them.
I like to use Hobbs 80/20 that is 80% cotton and 20% poly. For hand quilting I like Hobbs polydown or wool. Lately I have been using Mountain Mist Polyester for machine quilting because it does not shift during the quilting and drapes nicely.