I did the GA II in June of 2005 and it was perhaps the overall best liveaboard I've ever been on: extremely well-maintained and clean, good and diverse food, excellent service, and no complaints (I tend to be a nitpicker when there are nits to pick). Not only did they break down and clean all the SCUBA gear, but they even disassembled and sanitized the Draeger unit I had lugged down with me.
On the other hand, I've chosen the PH boat for this summer because they offer a 10-day itinerary and because I've heard it's as good or better than the Aggressors. It will be my first Hughes boat experience, while I've done three Aggressors in the past. This is the last year that anyone will be able to offer itineraries longer than a week due to new Marine Park rules. Too bad, 'cause if any place deserves a longer liveaboard itinerary, Galapagos is the place.