I took a hand quilting class from Roxanne (of Roxanne's Glue-Baste-It), and she highly recommended Fairfield's cotton batting. For hand quilting, she said it needed to be rinsed and machine dried to remove the sizing. For machine quilting, she just fluffed it in the drier.
She also showed us a quilt she had made using silk batting. That was her very favorite because of the softness of the drape. She said hand quilting silk batting was very easy too. At the time silk batting was very expensive, however, so she didn't use it for large quilts.
Harriet Hargrave highly recommended Hobbs Heirloom 80/20 for machine quilting. I have used it and liked it.
Mountain Mist Blue Ribbon 100% cotton batting is an old-fashioned type that lasts forever. I made a crib quilt with it that went through the washing machine many times. Saw it about 10 years later and, even though the binding was worn in places, the quilt itself was unbelievably soft and cuddly. This quilt crinkled up when washed and over time faded so it looked like an antique quilt.
Quilter's Dream is supposed to be excellent for both hand and machine quilting; however, I have heard it remains very flat even after washing.
A lot depends on what you are using the batting for and how you want the finished quilt to look. For example, machine quilting lines look very different on a quilt with 100% cotton batting vs one with thick polyester batting. Thick polyester battings can be extremely difficult to machine or hand quilt and are usually tied. Most hand quilters choose fairly low-loft batting, whether cotton or polyester, because it is much easier to quilt. When you want a flat, very stable quilt (perhaps for a wallhanging), Warm 'n' Natural is a good choice. (I personally find the drape of WnN too stiff for bed quilts and cuddle quilts.)
To make a good choice, you probably should consider first what type of use and look you want in a quilt. That will narrow your choices considerably, making it easier to research reviews on the ones you are considering. I would not recommend buying a lot of any one batting until you have used it in a quilt or practice piece and either washed it (to see what it looks like after washing) or finished the edges (say, for a wallhanging that will never be machine washed and machine dried).