I have the z9, and would like a second Mirrorless camera or replace my d850. If money is not the issue, would you set a second z9 or a z8? For those that have both, would you still have the z8 and z9 combo or would you do it differently and why? I know weight could be a factor, but what are other positives or negatives have you found with the use of both systems ?
The answer or advice is simple,
If weight and size is not an issue then 2 x Z9
If your doing a lot of video then 2x Z9.
In cases traveling or hiking where weight and size is an issue then a Z8 and Z9 but by the time you lug 3 or 4 spare batteries you might as well use a Z9,
The Z9 batteries and cards work in a D850 grip as well.
But before taking the plunge let the Z8 be out there for a few months first, in case there are issues that develop or need fixing etc.
I mean there is no shortage of Z8 units.
For my self, absolutely i would go 2 x Z9, i can share batteries, cards, one charger, more battery capacity, longer video performance, duel cards, no heating limitations, fully compatible card and battery with the D850 on a grip.
I am happy staying just with the Z9 and D850, i expect the Z9 II will come soon, also i prefer to focus on glass more than duplicating camera bodies.
The only thing left now is to make a choice that suits you.
A Z8 with a grip and 2 batteries in it is close to the Z9 weight, without the grip and just carrying 4 spare Z8 batteries is also close the the weight of a Z9.
Battery life is the last thing you need to worry about if your hiking or traveling. Plus you need to carry a Z8 charger as well.
Only an opinion