Interesting. The Hobbs website used to have a batting comparison chart; it is no longer there. They also used to have some kind of guarantee against shrinking for their Heirloom wool batting (shrinkage of less than 1%); however, I can't find that anymore either.
I did find an old copy of the Hobbs chart on a different website. Here it is:
http://www.how-to-quilt.com/articles/quilt-batting.pdf
What is still not clear to me is how Hobbs wool responds to machine washing and drying. I'm pretty sure it is very similar to cotton, with shrinkage of less than 3% this way. The big thing to worry about with wool, aside from shrinkage, is bearding. Hobbs wool is resin-bonded, which helps prevent bearding, but I still probably would not trust it with very dark fabrics.
From previous threads about wool batting, I have gathered that the Quilter's Dream wool has an odor when wet that goes away when dry. I don't think Hobbs wool has that.
What I would probably do is go with the Hobbs Heirloom Wool batting but maybe buy a crib size first, make a quick baby quilt with it, measure it, then machine wash and machine dry it and measure it again. If I liked the look, then I would use it in the big quilt.
One thing to avoid is off-brand wool battings. Hobbs and Quilter's Dream are the *only* battings I would trust. Others have reported extreme problems with distortion and bearding from brands I had never heard of.