Originally posted by KiloHotelphoto The Fuji is also a lot smaller.
It's a siginificant difference, but I think Pentax would say that their K-1 series is designed primarily for hi-resolution handheld photography, while the 645z is designed on the assumption that it is usually going to be tripod mounted. Fujifilm is closer to an all-purpose camera because they are trying to appeal to both kings of user in one series.
What I meant was that given what the 645z is, it is still relevant in terms of technology, even though it must be near the end of its product cycle and close to replacement by now.
There seems to be a lot of space in the 645z body behind the sensor plane and the back screen which most of the GFX cameras do away with. I think Pentax could and will reduce the size in the next iteration. But it's never going to be quite as small as GFX and neither does it have to be as long as the K-1 exists for handheld photography.