I upgraded from Lumix S5 to Lumix S5MKii although I had no real reason for it. It was just GAS (gear acquisition syndrom), because I wanted to see how the AF differed and I was afraid that if I do not preorder immediately, I will have to wait a long time. I mean, how embarassing is it to run a L-Mount forum and not having the first Lumix body with PDAF in your own hands?
At least that is what I told my wife...
Unfortunately I have not had much time to use it. I never had problems with DFD focus on my original S5. I tried videos and the PDAF is really better. I can do face-videos and move a little bit and there is no wabbling/pulsing anymore with the Lumix S5Mkii. It keeps the focus.
Unfortunately, there seems to be still a crop in 4k 30p with the S5 MKii.
My younger son is playing field hockey. I am planning to try the Lumix S5 Mkii with the Lumnix 70-300 and see how that goes. Very difficult sport for the AF, because there is no way to predict how the boys are moving. But to be honest, with a little experience in that sport, I was also able to get good shots with the original S5.
I think the S5 Mkii has faster frame rates in continuous shooting. I sold already the original S5, have too look at the data sheets on the net. FPS is more important for me in sports, to be able to catch the right moments when they shoot a goal or pass the ball to someone else. To find the right second when face, body, stick and ball are in the right composition you need high fps without a blackout of the viewfinder. Still a negative thing with mirrorless cameras.
For still photography, I do not think (at the moment), that you will see or feel a difference. I was planning to do more video work, so that made the decision easy for me.
I am still missing a dedicatd button/wheel to switch between spot metering etc., similar to the S/C/MF knob of both S5. IMHO this would have been important. Of course you can program this to another button. But why? 2100.-€ is not a piece of cake. If all brands increase every year the prices for new models, my expectations what has to be included and what that camera has to be able to do are increasing too
I do not know how the differences between S5 and S5ii is for high resolution shots. Maybe there is for you an important difference?
Viewfinder. Finally on the level of a Nikon Z6 et alii. The viewfinder of the original S5 was already very good for the small MP, but this is now significantly better. But still no MP like an S1R or S1. I would have loved to see a 5.7MP viewfinder in the S5 Mkii, but I guess they need something to differentiate for the successors of S1R and S1.
The S5 Mkii is bigger than the S5. Only a little bit, but I am notorious with body sizes and I felt this immediately. This would be an important point for me. Some say the grip would be better with the S5Mkii. I like both grips.
The AF joystick is a little bit better on the S5 MKii. You can easier change the AF point while looking through the VF. But there is still room for improvements compared to other brands.
This is all so far. Again I have not used it much yet. But I will update in this thread, if I find more differences which are worth to mention.
In my view, if you do not need PDAF and the better viewfinder, I would go with the original S5 as a second body. They are available very cheap now and I hope that 2023 will be the year in which all brands will push the market with more than one new camera model. Also Panasonic.