The above image was shot with the Nikon Z7 Nikon 50mm f1.8 hand held
I have now owned my Nikon Z7 and Nikon Z50 for just over a year. I bought the Z50 first with the 16-50mm Nikon lens and the 50mm-250mm longer zoom. Those are the lenses I still have for this camera. The Z7 I bought two days later with the 24-70 f4 ZS and then a few weeks later a 50mm f1.8 ZS lens. Both have run flawlessly as has every Nikon I have bought over the last 8 years. My previous camera set up before the Nikons was a Sony A7iii with 55mm f1.8 Sony Zeiss, 35mm 2.8 Sony Zeiss, and 24-105mm f4 Sony. Plus using a Sony adapter with several Minolta auto focus lenses that worked will with the Sony 7iii.
The Sony A7iii was a back lit 24 mega pixel sensor, Z50 is 20 mega pixel crop sensor (approx), and the Z7 46 mega pixels. The quality of the image from any of these three cameras using a lens of about the same quality is nearly the same. The Z7 has a lot more pixels and you can see this if you pixel peep close enough.
As you can see the sample photos are very similar for all three cameras. One of the key benefits of the Sony was that the native Sony 24-105 and 55mm Sony Zeiss lenses are just spectacular. Maybe the quality of the Sony 24-105 is not greater than the Nikon 24-70, but the additional range is much more useful. The other Sony advantage for me personally is that I had several really good Minolta lenses, a 50mm 2.8 macro, 100mm 2.8 macro and others. The 100mm is one of the best lenses I have ever owned, same for the Sony Zeiss 55mm f1.8. To my eye the 55 and that 100 were just a bit nicer than the highly rated Nikon 50mm f1.8. And I have to say the 100mm Minolta focused very fast with the Sony adapter.
To wrap up image quality I would say all three of these bodies give about the same results.
In addition to having no mechanical failures on the two Nikons for the last year I have also not had any card failures. So the fact that these two camera bodies only have one card slot has not mattered. That said, I preferred the two slots of the D750 and A7iii to the single slots of the Z7 or Z50.
For me using the Nikon bodies vs the Sony A7iii was a big improvement. The grips on the Nikons are much better for my size large hands than the Sony. But keep in mind if your hand is not the same size as mine the Sony might be better for you. I tried buying an extra grip for the Sony and that did give me a little more space to put my fingers, but I still much prefer the Nikon grips. In addition to grip the Nikons have better balance than the A7iii. The way the Nikon bodies and lenses are made just works for me better. This includes my Nikon DSLRs the D5500 and D750.
On top of holding the Nikons I also found the Nikon buttons, controls, and menus much easier to use. The Nikons both have touch screens and the A7iii does not. Touch screens are an improvement.
Video. Both Nikons do a very good job of video and so did the Sony. The Nikon switching control to go from stills to video is a much simpler system than the Sony. However, I have to add that I rarely do video with my cameras and usually use my iPhone. The exception to this is the Z50. Using that camera body plus the little 16-50mm zoom it is very very easy to use and switch back and forth from stills to video.
I find the Nikon Z50 to be an ideal family and travel camera. Most users should be fine use getting the two kit zooms and leaving it at that. It is much easier to shoot video with this camera than an iPhone except that the iPhone has a bigger screen – viewfinder. In full sun the Z50 has the regular viewfinder that is much better than a back screen.
Nikon Z50 and Z7 files are very easy to work with. The raw files and jpegs are handled well with Lightroom Classic or Lightroom. And Apple Photos does fine with the jpegs. The year I had the Sony A7iii the software seemed to improve. By the time I sold that camera it was possible to get very good results from it. On the other hand when I got the Nikons, right off they seemed much faster to get a finished file from. Plus Sony raw files are huge compared to the Nikon ones. The Nikon software is much better at this than Sony, or at least it was a year ago and Sony could have improved.
The Nikon DSLRs I had the D5500 and D750 were much easier / or you can say less confusing to auto focus than the Sony A7iii or either of the two Nikon mirrorless. In addition, the DSLRs had mechanical lenses and that type of lens is much easier to manual focus with than electronic lenses. The Sony was very good at eye auto focus. Fast and very sure. The Nikons are too, but the Sony is just a little bit better.
The two Nikon bodies are an improvement over what I used the year before. The Sony A7iii. This is much based on the fit of the grip in my hand, the buttons, controls, touch screen. I found the Nikon Z50 to work really well for family shots. The stills and video was very easy to use getting the people you wanted to focus on in focus. And with some software upgrades from Nikon the ability to easily find a subject and lock on to it works well too. If Sony were to fix the grip, controls, and menu, and touch screen I might be tempted to buy one again to see if it is good as the Nikons. But for now I am sticking with these current Nikon bodies for a while until something better comes along at a price I want to pay.
Mirrorless vs DSLR. There are advantages and disadvantages to both. I very much like seeing the histogram in the viewfinder of mirrorless cameras. I like that the video of mirrorless is incomparably better than the older style DSLRs. But I prefer the always on optical view finder of a DSLR. I prefer mechanical lenses when shooting stills. For video if you want to autofocus electronic lenses are better. I much prefer the long lasting batteries of DSLRs. I prefer the many buttons for specific tasks you get with DSLRs. With my D750 I could find most of the function buttons without looking. Having things like a specific bracket button is very easy and faster. Nikon has done a hybrid DSLR-mirrorless with the D780. I have heard that next comes the D880 with at least 46 mega pixels and maybe in body stabilization. That would have optical viewfinder and then the mirrorless style video using the back screen. Since I almost always use the back screen for video that would work well for me. I am eager to see what comes from that. I have come very close to getting a D850 over the last few months in addition to my mirrorless bodies, but decided to wait to see it they updated the D850 like they did the D750. I think if it comes out at a price I am OK with, I will get one.