My choice would be Hobbs wool. Quilter's Dream wool is also supposed to be good, but at least one quilter on the board here posted about some problems with it so I am inclined to stay away from it. I would ***not*** buy any other brands of wool batting or use old wool batting, as they may not be manufactured with the new standards for wool. Old wool battings had to be encased (by the quilter) in cheesecloth before being layered into a quilt; otherwise they bearded terribly when quilted. Off-brands of newer wool batting may require much closer quilting (and possibly also layering in cheesecloth) to prevent weird distortions when washed and bearding.
Wool batting (Hobbs or QD brands) is easy to hand quilt or machine quilt, gives excellent stitch definition to the quilting (probably the best of any type of batting), has good loft, "breathes" well, is washable, and basically lasts forever. It is often the batting of choice for people who make quilts with hand applique and want to hand quilt -- because it gives such good definition to the quilting.
If you scroll down a bit on this website, you can see an example of quilting with wool:
https://sewkatiedid.wordpress.com/ca...l-color-quilt/