"Best" depends on what you're looking for (cheapest, best location, easiest parking, boats, etc). Here's my quick take on the four dragon boat facilities on False Creek:
DBA (just east of Cambie Bridge) - Don't know much about these guys. They have those nifty

teak and Taiwanese flag catching boats, and I think I've seen people paddling those half-sized 10 person dragon boats out of DBA.
Dragon Zone (next to Science World) - Best location for public transport. Biggest dragon boat fleet.
FCRCC (Granville Island) - Best for cross training outrigger, marathon, kayak, or other canoes. Best facilities thanks to False Creek Community Centre. Worst parking (although DZ and DBA may face some challenges with all the construction in their areas).
Pogue Sports (next to Burrard Marina) - Great parking except during Bard on the Beach. Run by the ebullient Ryan Pogue.
Disclaimer: I'm an FCRCC member and this is my entirely subjective opinion.