The G9 with fiber optic cables will provide a TTL capability. At least it does so very well indeed with my rig...
Really??? I get what Sergio is saying, with the direct connect you get "True" TTL....do you get the same with the FO? I ask of course because of the fact, even admitted by Sea and Sea, that what the DX has is not true TTL with the FO setup.
Another plus like someone mentioned here...maybe Sergio? and also have talked to Chris about it, is the compactness of the DX. If I choose to do a shallower daytime dive.....I can just stick it in my BC. OR...use it for closer shots with a dive light. But that compactness is a nice plus for sure, compared to lugging the Ikelite case on every dive I want to shoot anything.
It's also hard to say at this point...what will entice me more? Reg scenic type shots, or more macro. If it's scenic....then the G9 is 35mm - 22 with addon WA. The DX is 24mm and 16mm w/WA add on, "SEEMS" to offer the better option.
But hey...I'm a noob...so if my train of thought or conclusions are off here...please don't hesitate to point it out!! 
Cheers,
Greg