The title suggests I'm not capable of making up my mind. And yes, in a way it might be the case. Because these two brands are not the only brands I came across (during many years that is). But in my situation, is just about these two systems.
A few years ago, the Sony A7R was announced. At that time I was using a micro four thirds system. (Olympus OMD which was blazingly fast, and in that regard, years ahead.)
But since I really liked a full frame system, I sold my Micro 4/3rds system for that A7R. Long story short. After a while I really hated the sluggish auto focus of that system. Shortly after that I bought my first Fuji X-T1 next to the Sony because I simply was looking for alternatives because the Sony A7R was just too slow.
The first wedding shoot I had I made use of those 2 systems. And it became clear that after that day, I only had used the Sony for a few shots, but used the Fuji XT-1 for the rest of the shoot. So, sold the Sony and never looked back.
I really was a happy Fuji user from 2014 until mid 2018. In the end I used the XT-1 and the X-Pro2 with a variety of lenses. Especially the 56mm 1.2 for portrait work.
Of course I saw a lot of systems coming by, but to me only the Fuji X series where the holy grail when it came to the mirrorless photography world. Yes, I saw much news coming by regarding the Sony systems, but I really had such a dramatic experience with the first A7, I never really paid much attention to that news.
"Full frame" still was floating in the back of my head. But a proper, affordable, mirrorless full frame system wasn't available in my eyes. Then the Fuji GFX turned up. As nice as it is, to me it seems that it's a very specific system you just don't carry around outside of a studio. Yes, that might be my narrow minded view, but to me it just looks that way. Then again, it's not cheap either.
During the release of the GFX system, again Sony also stepped up their game with the A7 series with the swift iterations they made. And with the third iteration, you couldn't just ignore the major improvements they made.
Now, I just sold my X-Pro2 for the Fuji X-H1 and really was a bit disappointed in general. Especially having to buy quite some batteries to get me through the day. In no regard, except for the stabilisation, it was an improvement to me. (No shooting video isn't my thing.)
Yes, one could argue I could have spend some time checking out the reviews seeing that I really should not have expected a big jump there. But it did made me think hard, about a full frame option called the A7III.
I really took the time to decide if I should make the switch. Since the Fuji's really served me well. It's a system that in many regards has a lot of plusses compared to the Sony alpha system. Also I couldn't find that much recent and interesting stories regarding making the switch from Fuji to Sony.
Now, since I finally did decide to make the switch, I can tell you I'm not sorry that I made that call. I really appreciate that I did. It's AF system is fast, has a hell of a battery life and has very nice (native) glass available too in my view. Especially having used the Fuji 56mm 1.2 that much, the 85mm 1.4 GM feels like a whole other level.
Having said that, it's still not a flawless system. But than again, which system is. The main issues I have with it, is that also that 85mm can struggle to focus in less ideal situations. But that eye AF is very, very slick. Made me take shots I really could not taken with my Fuji system.
And having a menu system that isn't as good as the Fuji, has it's upsides. It really makes you dig into the system and the available options. Looking for answers on Youtube and applying them to your workflow makes you more aware in a way I just wasn't with another system. So making it you to think more in a few occasions, might not be a real issue at all...
To be clear. If I wasn't into getting back to a full frame mirrorless system. I definitely would have stayed using Fuji. But since I was, making this switch almost feels logical.