I would vote for Cocos after my one experience with them (2005). That's the only Aggressor trip I've done that I didn't feel measured up to my Aggressor fleet expectations. Excellent crew, but many boat issues.
Galapagos II, Palau, and T&C were all excellent, if not flawless (when I can't find a single thing to complain about, that's flawless IMO). Some minor issues with the now defunct Tahiti boat. My only Dancer was the Sky (Galapagos) and they've since defected. I had mixed feelings about that boat (minor crew issues, two major cabin issues), but as they're combined now, I wouldn't "boycott" Dancer over that one experience.
My non-Aggressor/Dancer experiences range from excellent to mixed. If I had absolutely no intention of doing any pre-trip homework whatsoever, I'd probably feel comfortable jumping on any Aggressor or Dancer boat. I wouldn't trust an independent, except for the handful of boats our there that have deservedly wide-spread excellent reputations (Truk Odyssey, Nai'a, etc.) unless I did plenty of homework. Even with the widely reputed ones, I'd still want some recent updates. Boats can change, crews can change, owners can change.