I have the S 006 and just spent a few weeks testing a GFX that a friend lent me. In terms of quality of output, they are not so far apart. Personally, I found the S to have more pleasing color, while the GFX had a slight edge on detail and snap at times. I felt that the raw files looked like they had 10 more points of clarity than the S. (Adding 10 points to the S made them extremely close). I think this is just how they have decided to tune their RAW output. The files were done in Lightroom. I found that the 63mm lens in the Fuji was excellent and sharp in nearly all situations. The 70mm from Leica has a bit more pleasing bokeh, but on landscape images it is a bit trickier to handle at times if the subject matter is very distance, as it has some field curvature (the sharpest areas are not equidistant to the camera). I would prefer the Leica 70mm for portraits. Personally I much prefer the handling of the Leica S, both in the interface and in the optical viewfinder. The EVF in the Fuji is not what I would consider great...both the A7Rii and Leica M10 EVF seem better to me. The interface in the GFX is not bad, and there are some nice touches, but I prefer the way Leica has set up the S. Tastes differ. In terms of sheer quality of output, given time to tweak everything in RAW conversion, I would give the edge to the GFX. It is, of course, something like five or six years newer. But if you asked me which camera I would prefer to use and work with, it would still be the S by a mile. The GFX is where the future is headed, but I still think there are too many compromises, especially around the EVF, which is really critical -- the viewfinder is our contact to the subject matter, it needs to communicate a huge amount of information more or less instantly and with as little disruption as possible. I have yet to see an EVF that could do that satisfyingly, not even from a camera like the SL. Meanwhile, SLR's, RF's and large format cameras do this nearly perfectly. I take the best pictures with the cameras I feel disappear in use...cameras like a good 4x5 camera, Mamiya 7ii, Leica S, Hasselblad 200 series, a Konica Hexar....all those cameras don't get in the way of the relationship between the photographer and the subject. For me all the EVF cameras I have owned or used could not meet that criteria. They might have beautiful output and a lot of great things going for them, but at the end of the day, you are still watching low quality screen image of the subject, as opposed to the directly reflected, unfiltered light coming off of it. I think this is not that important for everyone. For me it still is.