The new GW was designed to be a high end material park board that shares it other specs with the Airobic. There is carbon between the bindings which stiffens the mid section a bit and adds immediacy to the response there as well. It gets a sintered base and the hardwood stringers move from the center (on the Airobic) to edge (on the GW). Bataleon lists the flex as the same for both models, but the GW feels (a little - OK, very little) stiffer.
The ET is a more powerful deck, but I would still hesitate to call it on the stiff side. That will depend a lot on what you have been riding. So...What have you been riding?