Well each to their own and all that. You mention having to use Capture One for Fuji, you don't, there are lots of different apps out there, even Lightroom has it better these days [Still a dog for speed IMO though]. And what is it in the free version of Capture one that 'wasn't appealing' for you? I think it does everything you need, unless you want to work in layers or tether to a camera (a must for me so I use the full version, as I have for years), it's pretty much the full version only costs nothing...
I guess if you spend your time pixel peeping into your images and want the absolute best in IQ then it's easy to look down your nose at some cameras or find that they are not for your particular analysing every image needs - I feel like that sometimes too after a day of shooting with a proper full frame camera with it's 54x43mm sensor, but I still prefer using the Fuji cameras, the X-PRO2 is my favourite day to day as I like the feel of them and in reality no client of mine has questioned my choice of gear once. Like I said each to their own but perhaps I'm lucky with the photography I get to do.
Andrew did you get to play with the X-T2 and 50-140 yet?
iirc he's getting the fuji xt2 and 50-140mm almost giveaway cheap price.
If he shoots with a 5dmk4 with his current 70-200 f/2.8IS mk2 he'd be very familiar with the "look" of his 5dmk3. The difference is a noticeable bump in image quality, high iso capabilities and overall performance from the newer digic processor. In lightroom I can tell the difference between my aging 5dmk3 vs my 5dmk4. The difference is almost like upgrading my lenses......No need to pixel peep as the image quality is very obvious and better in low light than the sony crop sensor inside of the Fuji body. I have no need to pixel peep knowing I'm getting incredible high iso capabilities in the FF sensor world. I'm fully aware of the files I've obtained by smaller sensors I've owned and used extensively over the years.
I often find more and more hired photogs simply accepting average IQ even though they know it's noisy. Generations back it's more acceptable in the 5dmk2 era. 5dmk3 simply improve a bit more. Tech these days has really ramped up as incredible high iso performers in the FF world. aps-c sensor improve laterally to FF. Crop will never surpass FF. On the same note FF will never surpass medium format or in the fuji GFX world "large format sony sensor".
Few will dare to shoot an entire wedding or large event coverage with a GFX 100MP sensor. Even current high MP bodies such as the Canon 5dsR or A7r3/4 or Nikon D850 can go through many memory cards and slow down the work flow in post processing with huge files.
Andrew is curious how the fuji will hold up in concert lighting. Fuji will fair well since a good percentage of the time the lighting is easy. So if a modern aps-c does well in that lighting a modern FF will be even cleaner. However when the light gets challenging crop sensor photogs excuses will pop up why their is obvious more noise with a smaller aps-c sensor vs larger more capable FF sensor in low light. My real life comparison of my former X-t2 vs my Sony A73 is a world apart in cleaner files with Raw files that no longer fall apart at high iso vs my Fuji. If my X-t2 matched my Sony A73 low light performance I'd still keep the Fuji system.
Sony A73 will have cleaner files than a Fuji X-t2, X-t3 and this is doesn't even require pixel peeping. It's a photogs choice in selecting tools. A Nikon D850, 5dmk4 would have cleaner files across the board in challenging light. Now this becomes the photogs tolerance to noise and what he/she provides their client.
After using my X-t2 with 50-140mm. Hands down the IQ I provide family/friends/clients with my FF gear with Gmaster 70-200 or Canon 70-200 f/2.8is mk2 are better than my Fuji setup regardless of what light I am dealing with. However if i'm shooting easy light the Fuji x-t2 with 50-140mm does well if it's not challenging the sensor. Only downfall is I notice the difference between f/4 dof using an f/2.8 zoom wideopen using aps-c vs FF Dof.
If I was a hired shooter for concerts I'd definitely be using my A73 or 5dmk4 that I have in my gearbag.