(Disclosure: my gear closet has been substantially downsized, and is now all Z-system mirrorless)
A viewer question came up during the on-line African Safari seminar Mark Comon and I presented last week. To put the question in context, the safari trip we were talking about had 17 students and 3 instructors over a course of a month, and there were 36 Z8 or Z9 bodies being used on the trip (also 3 D500s).
Here's the question re-phrased: "So is there an advantage to using a mirrorless camera over a DSLR on safari?"
Yes, but it's not at all related to most of the things you might think (image quality, focusing, etc.). Most of the photos that were taken by the students—estimated to be over 500,000—could have been as easily taken with a Nikon DSLR as with a mirrorless Nikon. Indeed, some were (the D500 images).
So what's the "yes," then?
It's a lot of nuance things. The Z8 and Z9 bodies have faster frame rates than the D500, D850, and D6, so if you're photographing in bursts you get more choices when you go to pick a frame. Pre-release capture removes the need to anticipate, at the expense of switching to JPEG. The CFexpress slots in the Z8 and Z9 write the entire buffer quicker than the XQD/CFe slots in the DSLRs. Your exposure and white balance show in the viewfinder on the mirrorless systems, and this is without frame blackout while taking a burst.
You might have noticed that I wrote that there wasn't an advantage to focusing on the mirrorless cameras. That probably surprised you, since Nikon has been touting the Subject Detection and other autofocus abilities of the Z8 and Z9 (and tends to downplay the focus abilities of their best DSLR, the D6).
To me, focusing is different with the mirrorless cameras than it is with DSLRs. That means learning new things, taking different levels of control at different times, and getting the camera properly customized to that. I certainly never had any significant focusing issues with the D6, nor do I have any with my Z9. But they act and operate differently, which means that I have to control them differently.
A lot of DSLR users are worrying that they're missing out on something by not transitioning to mirrorless. They are, but it's minor things and nuanced things, mostly because the mirrorless designs are newer and incorporate new ideas that weren't around when the last DSLRs were designed. In terms of out and out performance superiority, there is none. A D500, D850, or D6 that's well learned and handled well could have gotten virtually any of the photos that all those Z8s and Z9s got during our Africa trip. This suggests that there's no urgency in transitioning if you've already got a top DSLR system.
Bonus: One thing I noticed in going back through a lot of material working on book updates is this: the last update for the Auto distortion control system was 2.018. Curiously, Nikon removed the date that was produced (hint, the last macOS supported was Catalina). This tells me that the decision to go "all mirrorless" for lenses was made quite some time ago, as that table of data has to be in the mirrorless bodies (to work with the FTZ adapter), and there's no known mechanism for updating that. Perhaps Nikon could have updated every Z camera with a new table internally if another F-mount lens was produced, but that's a lot of extra work, so I'm pretty sure that the 120-300mm f/2.8E in 2020 was the last F-mount lens Nikon intended. This implies that Nikon's decision to go all-in with mirrorless probably came shortly after the Z6 and Z7 in 2018. We're six years past that now, with only two DSLRs having been introduced since (D6 is 2019, and D780 in 2020).
