Interesting so, I tried both cameras and according lenses already last year and the Panasonic simply became totally uninteresting when holding it in hand. Totally turned me off, while the Sony (A7R4) was beautiful to hold and handle, even with bigger FE mount lenses.
Add to that the definitely superior AF and for me the decision is clear as crystal - never buy a Panasonic combo and better go with Sony if really FF is what I want.
Having said that - I had another very telling encounter some days ago when I was able to test the X-Pro3 with some different lenses. Man, I can tell you all that I went out of the store and knew I maybe would never ever go FF again, as I loved holding and shooting this camera so much - much smaller and unobtrusive, fast, stealthy and that new beautiful screen in the back that is obviously really what I always wanted but did not know. And whatever Fuji lens you mount on that camera it simply is beautiful to hold and handle - WOW!
Yes... everyone has subjective differences and in no way am I prepared to make a definitive choice for others. I still have and use my Sony kit and there are some clear performance related benefits that are head and shoulders above the competition. Autofocus is the biggest one of them. I don’t have a problem with the newest Sony body but is still don’t feel like it’s wide enough or y’all enough without a grip for my own hands with the largest lenses. For me the S1R is far more comfortable without a grip (which I don’t own) and the deal that I received (less than 50% of the new price) made it a no brainer for a camera over been eyeing for over a year despite trying nearly every other camera on the market in that timeframe. I will still run a Sony kit for pro work and when the base level body switches to the newest body style I’ll probably switch all of my existing bodies for the A7IV. 24 megapixels is more than enough for my pro work and the Tamron f/2.8 zooms that I’ll use on the Sony bodies are very good lenses. I’ll primarily be using premium prime optics on the Panasonic as I view it as my “personal camera” for my creative work.
I would actually love for Leica to allow Voigtlander into the official L-Mount family for those that love smaller manual focus primes that may not want to pay Leica prices or don’t fully trust DFD/CDAF based systems yet. I’ve said in the past, and still believe, that DFD will eventually get to a place to where the processing speed isn’t a detrimental issue with wide aperture lenses. Maybe we will see that in the next generation round of cameras but I have it on great authority (from someone in the know) that this will all come down to Panasonic’s commitment to the development as they may have as much of not more invested in L-mount as Leica in reality. For instance the Sigma fp has internals and batteries made by Panasonic, it was suggested to me that the Venus Engine, Leica Maestro, and the Sigma Image Processor are largely the same exact base part with company specific software baked in to give them all individualized looks... but underneath it all that’s the strength of the alliance. If offsets much of the development costs so that each company may not need to seek as much product of say a Sony, Canon, Fuji, or Nikon for their camera divisions to remain profitable.
Again, this is subjective desires and the Panasonic S1R solves a lot of my complaints with the Sony... but for a new photographer I’d suggest them start with the Sony. It’s easier to use and is more reliable to use in the automated modes. Ultimately people want to be able to get the shots they are attempting to take and for a new photographer, to lose confidence in hardware, would usually mean they’d stop using the camera or just use a cell phone camera. Would I love for DFD to be as rock solid as Sony Hybrid Real-time AF? Absolutely... if it were that good I wouldn’t own a Sony any longer but it’s not there yet today. It’s better than many say but there is something to OSPDAF affecting the maximum IQ. Again, that doesn’t mean that those cameras are incapable of great IQ but the S1R does have a higher level of acuity than say my A7RII... but this will mostly matter when pixel peeping. Nothing wrong with any of these cameras and once I came to terms with the reality that the decision isn’t about either or but rather this and that then there was less internal consternation. I realize everyone doesn’t have disposable income for camera systems that cost in the thousands much less two separate ones but there truly aren’t one size fits all solutions anymore. For someone starting fresh on a budget I almost always recommend Sony first. If someone is coming from Canon or Nikon I encourage people to look at their Mirrorless systems with the understanding that eventually they should sell their DSLR lenses if they plan to do video. If a person is looking at video primarily - I lean towards Panasonic first with the caveat that Sony or Canon are a great option if a person has a larger budget for the higher end cinema/ENG style cameras. Again Nikon is working themselves into this space and I prefer the Z6 to the Z7... I think it’s the sleeper camera in their lineup and can be had for around $1500 body only. For a person that doesn’t want to do editing Fujifilm is great and the GH line is still respected in professional circles. People will argue over 8-bit vs. 10-bit color but spec sheets often don’t provide nuance - intentionally.
That’s a discussion for another day