Not sure of the specific differences, since there are no detailed reviews yet. It looks as though the Hybrid is a bit less massive than the Dragon; I noticed that the sides wrap around lower under the arms, for example. It's my impression that the Hybrid is more portable. I would also be curious to know if there are any features in the Dragon that the Hybrid doesn't have. It does appear the Hybrid can be used with the optional Mares octopus, like the Dragon.
But so far I've been unable to buy it. New York City's largest and most popular scuba store, Leisure Pro, didn't even know it existed when I visited on February 6th. This is a shame because I need to replace my trusty old Zeagle.