I have owned both the DS II and DS I.
The DS II is heavier and with a higher center of gravity. E.I. it capsizes easier and is harder to right when it does. The inter hull will always fill with water, its a pain to drain unless you can pull it on your trailer.
The hull seems to be thinner, that makes them more flexible with very little way to stiffen them. Stiff hulls sail faster. The DS II is not as comfortable to "hike out" on for long periods of time when over powered.
Gus Heismann (marktdes-at-oneimage)