Valiente,
Thanks for the sanity. If you are actively sailing, nothing comes close to the output of the water towed generator. Duo-gen has a plus as it is convertable to wind generation for at anchor charging. I would regard it as a more reliable source of charging as well, because it will be charging when you really need your batteries up, underway. If your bank is down at anchor it's generally not a crisis. If you're running low at sea it can be a problem.
I found my way to the three manufacturers via this site:
http://www.onpassage.com/Alternative...generators.htm