I have not hand quilted with wool or silk but the higher the cotton content of a batt, the more it "grabs" the needle. If you want to load your needle with lots of tiny stitches the cotton hinders pulling the needle through. Wool will be puffier and harder to load a needle so I think silk would be your best option for tiny stitches.
However, if you are doing the big stitch method of quilting, you can use any batt.