I prefer cotton over polyester battings every since I made two quilts -- one with poly, one with cotton -- for my niece and nephew. I happened to see both quilts many years later after they had both obviously been through the washing machine many times. The poly quilt was in terrible shape with the batting in lumpy balls throughout. The cotton quilt was soft and wonderful even though the binding on it was worn through in places.
For machine quilting, I like Blue Ribbon brand 100% cotton, which is the batting I used in the quilt above. (I hand-quilted it, which is a mistake with this batting.) I also like Hobbs Heirloom 80/20 batting (80% cotton, 10% polyester).
For hand quilting, nowadays I would probably test out Quilter's Dream or Fairfield 100% cotton (rinse and spin dry before using for hand quilting), as I have heard these are very good.
I don't use Warm 'n' Natural anymore because its drape seems stiff to me compared to other cotton battings (probably because of the needle-punched scrim). I did use it for quite a few years, though. It washes flatter than other cotton battings.
Not everyone likes the flatness and crinkliness of cotton battings. I think many people these days are used to comforters. To get a similar effect in a quilt, you pretty much need to use a polyester batting. I like the antique quilts, which are mostly the thin and crinkley kind because of their cotton batting. Once in awhile, though, for a wall hanging or specialty quilt I will use Warm n Natural or a polyester batting for their effect.