Okay, I've gotten all of this information second hand, I've never attended either festival, but from what I understand (and can remember, I haven't done a festival in a few years, time and $$$ issues) Sirius rising is the "family friendly" version of Starwood. Starwood is the real party (less family friendly).
Family friendly, in pagan/semipagan circles, means generally: nudity optional, public sex is verboten, the partying (read that any way you want to) is more subdued and ends early in at least some part of the camp. "NON" family friendly means: nudity optional, public sex is possible, the partying can be heard all over camp and goes on until 4:00 a.m. or until people collapse.
Sirius rising grew out of the fact of people having such a blast at Starwood that they wanted the festival extended. Sort of an overflow festival
