If you've been to a Sigman workshop and it seemed familiar, then I would highly encourage you to attend Dan's workshop because Daito ryu aiki is different (I'm NOT saying it's better or worse, just different). How? Go to the workshop and not only feel/experience it, but get answers.
Because you brought it up, apparently to encourage people to ask Dan's permission to attend this workshop (and because you've seen Mike Sigman), please describe how Dan and Mike differ, and how Daito Ryu aiki is different from what you believe that Mike does.
Also, are you saying that Dan is demonstrating and teaching Daito Ryu aiki? If so, how does his Daito Ryu aiki differ from other Daito Ryu approaches (for example, that of Okamoto-sensei)?
I look forward to your reply.