I haven't used silk, but I did handle a quilt with silk batting in a class given by Roxanne Elroy. Silk batting was her favorite for hand quilting. It provides a very luxurious feel, and the resulting quilt is very light in weight and is supposed to be cool in summer/warm in winter. It is supposed to be very easy to hand quilt.
I have hand quilted Hobbs 80/20. It's probably not quite as easy to quilt as silk, but is still very easy. The biggest difference I noted was loft. Hobbs 80/20 has more loft than silk.
If I had to choose, I'd go with the silk.