Noting my obvious biases, I'll just point out a thing or two regarding Dumpshock:
First, Dumpshock has the misfortune of having been the main discussion forum during some very controversial periods for the SR line (which I won't go into at length). It should be understood that as an online community it was made up of some of the games most hardcore fans who watched dramatic changes to the game they love and the alienation of certain developers and authors who were integral parts of the community. For better or worse (and whether you agree with their assessment or not) that has colored the modern opinions of that community about the game, the current editon and the current development team. They didn't choose it, although there is certainly some self selection at work now-a-days.
Second, in an ironic turn of events many people left DS and came here because "DS is too negative" while simultaneously many others left DS for places like the Gaming Den because "DS is nothing but a bunch of fan boys." The end result is that if you can get past a few bad apples (every forum has them, including this one), DS actually tends to be a fairly moderate place.
Third, the real strength of DS is the depth of content that comes from decades of discussion about the game and the setting. DS is an evolution of the very earliest online fan communities, so the people and ideas there predate the site itself (going back to the old Undernet #shadowrun irc chat community). Many of those people were pivotal in the develop of the game during certain time periods (people like Adam Jury, Pete Taylor, Bobby Derie even Bull). So yeah there is a lot of stuff there that relates to mechanics of old editions. But there is far more setting and fluff content there that transends editions alltogether. I would venture to say that I haven't seen a fluff or setting question in a long time that hasn't already been done in some form on Dumpshock.
So which forum is best? Depends on what you're looking for. None of them are what they once were. But lucky for us there is no law that says you can't be part of both (I frequent the whole spectrum of boards lately, including the Gaming Den). Personally I think all this acrimony about which board is good and bad has actually hurt SR's online community. I miss the days when there was such a rabid SR fan base online that you couldnt read the forums fast enough to keep up.