If the G 5 case is substantial enough to be shipped checked luggage and can survive the conveyor belts etc. then that would be a plus over my Pelican 1640. Although it is build like a tank, and seemingly crush proof, it does weigh in the 30 lb range and with the 32 lb weight of the camera the added shipping is surely a chunk of change... so far I haven t flown with it but am planning to hit the east coast which would be an airline trip. A road trip is planned for the midwest and then down to the Florida Keys.
Side note: I use an Offshore Angler cordura case, designed for fishing gear for 8 x 10 (Wista)carry-on and it works ok. They are made in various sizes. The one I have is 18 x 22 x 8, however padding is minimal.