It looks like the radial Hydranet is woven with a combination of Dacron and Dyneema in the weave rather than laminating the fibers onto a sheet of mylar etc.
They claim that the Dyneema gives strength in the warp direction and allows the sail to be cut with a radial layout.
Looking into it further, it seems that there is a disadvantage in that I suspect that it might be more difficult to find someone who knows how to make repairs or adjustments with this fabric.