The fixed lens ones are way better and more reliable. For the cost of the G camera with two lenses, you could buy two separate GW/GSW cameras. I owned both of the latter. If getting the GW, the first version is made out of metal, so more durable. I think version 2 and 3 were plastic casings. Just look for a camera with a low roll count.
I have since revamped most of my medium format film gear, since my first post in this thread. I no longer have the Fuji 6x9 cameras, the Mamiya RZ, and either of my Pentax 67II and 645N. Got rid of all of them. Pairing it all down to lesser cameras- to the essentials. I still have my Zeiss Ikon 6x9 which I used today, plus my Holga and Yashica 6x6 TLR. I kept half of my Pentax 645 lenses, so I can use them on my GFX camera. And I kept all of my Pentax 67 lenses, because I just got myself a late model (3rd revision) of the first version of the Pentax 67. I found the 67II too unreliable, and not as dependable in cold and wet climate. The version 1 is perfect for that use and is rock solid reliable. That camera is coming. To replace the 645, my intention was to get a Mamiya 645 AF or AFD, so I could have the removable backs and still have autofocus lenses. But that purchase may be a long way away, because prices on this camera are way up there now.