I own both the Fuji GFX and the Sony R7ii. You will have to make the decision yourself, as you note, but here are my observations:
A. I much prefer the GFX to the Sony as a general proposition for a number of reasons. First, the menu system is much simpler. Second, selecting focus points is easier. Third, I think the photographs have more detail and are richer. Fourth, I like the native aspect ratio, which works better for 17 by 22 prints.
B. If I am shooting in low light, I prefer the Sony. ISO 1600 is my limit for the GFX, although when caught by unplanned circumstances, I will go to 3200. With the Sony, my preferred limit is 3200, but 6400 is pretty good.
C. I find the GFX more comfortable to shoot with than the Sony, particularly when the 70-200 is attached to the Sony--although not an entirely fair comparison because right now native lens for the GFX is a 120. I am more than happy to walk around with the GFX and the 120mm lens for an entire day. Very comfortable. The lenses are big, but surprisingly light.
D. If you are looking for zoom lenses and greater lens selection, the Sony has the obvious advantage. But Fuji has released a roadmap with several more lenses scheduled over the next year. One will be a long lens or long zoom according to reports.
E. The Sony has an obvious advantage if you are sports or action shooter. GFX is weak on the autofocus, often hunting in lower light. I find for urban landscapes that that is not a problem. I have covered a fair number of demonstrations, and I get excellent results, but I have learned that autofocus is not fast enough in certain situations (a crowd moving toward you if you are in front of the march). I usually have a second camera with me for those situations. The Sony iii is supposed to be great with the face recognition, so if you are shooting action shots involving people, that my be a consideration.
F. The GFX has more shutter lag than the Sony--at least that is my perception--which has been a problem in concert halls. If the light is good, I still go for it, but there I do miss shots. For example, I think that I have the singer looking in my direction, only to find that I captured the singer turning away. Anticipation becomes critical. I always have a second camera for concerts, and I usually get my basic shots with that camera. Lately, it has been the Sony.
G. Overall, I think the Sony has more features and capabilities, but most of those I don't use. To some extent the Fuji is akin to a Leica M philosophically.
H. The Sony battery life is terrible. I find the GFX to be better, but Sony has apparently fixed the issue with the iii.
I. I like the Fuji dials for ISO and shutter speed and their placement.
I will be headed to Europe over the holidays. My walking around camera will be the GFX. I will take the Sony with the 24-70 lens as my backup. If you have any specific questions, I will be happy to respond.
These are my views after nearly a year (I think I got my GFX in January) of using the GFX three to four times a week. Others may have different opinions and views. Good luck.
