My recommendation, as it was in the early 90s when I got heavily into photography, was Canon over Nikon. Canon had a big advantage over Nikon during the early days of DSLR (early 2000s). With modern mirrorless, the choice is harder, but it's between Canon and Sony with Nikon being a distant 3rd and maybe even 4th to Panasonic depending on the use case.
Oh, forgot to answer that, but my personal Recommendation is usually to go Nikon, especially for General Purpose Glass or if you just start out and just need any Camera, as even the G-Style F-Mount Lenses will allow full Control over Zoom, Focus, Aperture (correct Adapter being assumed), and have the Longest Flange Distance of common Camera Systems.
So if i start out with Nikon F, i can still go with a Canon Body later if i wanted to, and use my lenses on there (talking DSLR/ F-Mount/ EF-Mount), while the other way around just wont work.
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Mirrorless Systems are a Whole other Beast, which i am still not sure what to say about, but i highly expect none of them to survive for even close as long as F-Mount or C-Mount/ M42 did, and all of that Glass to become more or less obsolete sooner or later, because Camera Bodys will be outdated at some point (just look at vintage ENG-Lenses and CCTV-Lenses With electronic-only Aperture Control, nobody really wants those anymore today), and Lifespan of Camera Systems Might not be that long.
Biggest Problem with Most Glass For Mirrorless Systems is however, because they are Mostly only Focus-By-Wire and Aperture-By-Wire (or at least one of the Two usually, some even Power-Zoom Even). And that means, there is no real Intended Way to use them without the Proper Camera Body they were Built for originally. So you cant just take any Fuji-X Mount lens and put it/ use it on an Chronos, even if building an Mechanical Adapter wasnt an issue.
So sadly, quite a bit of those really nice Mirrorless Lenses we have around today will end up as Expensive Waste at some Point in the Future once their Camera Systems died i guess, or will need to be Rehoused or something, unless Someone is actually going to want to go through the Trouble of figuring out all of the Digital Communication that is going on between Camera and Lenses, and trying to somehow trick the Lens into thinking there was a camera there actually, when there is not.
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Kind of a Difficult Topic, and only time will tell, what will happen to all those Mirrorless Lenses Made today in lets say 50 to 100 Years, and if you have any Mirrorless system you basically have to get a bunch of those Autofocus Lenses for that System if you want to use it to anywhere close to its full capacity, not really a way around it. Especially for Photography Purposes.
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So my General Advise, like i already said, is to go Nikon F-Mount, if you just try to build a Decent Kit of (manual Full-Frame) Lenses for General Filmmaking or Manual Focus Photography (or AF even, if you want to go with an Nikon Body), as they just fit onto about any Camera besides maybe Pentax K-Bodies and will be usable very long Term.
If you go for something more particular or need /heavily Rely on Autofocus and Stuff like that for Your kind of work, of course go with whatever your Camera System of choice Offers. Especially for the Newer Mirrorless Systems there are Plenty of new Lens Designs, that just were completely unheard of in classic DSLR Lenses, for Stuff like that you obviously also need with whatever you can get, if you can find any use for it. But while i love My Mirrorless 1Nikkor Lenses, and Probably would never sell them, unless i had to for some reason (they are just so damn nifty and Nimble Small, sharp Lenses. Easy to put into your Pocket to do some real low Footprint stuff (People will legit just ignore you with an ridiculously Tiny shiny silver camera and assume you are an tourist or something, which can be very useful at times...), and even have a Full kit with you, which takes up less space than an Full-Size DSLR with a Decent Zoom Lens on it), i still heavily prefer any lens that allows me full control over all Settings on it without the Need of Electronics being involved.
