Nikon D850+500 PF or Canon R5+100-500 - better for birds?

jwpvb wrote:

To me, trying to work with two different systems, eventually compromises the performance of both (may be some people can), not to mention the need for two camera bags.

Well, I own something like six camera bags, and usually have my wildlife gear in a different one from my landscape/architecture/other subjects one, taking either or both along as needed.

If you are used to having one main body, my approach won't make much sense to you, which is perfectly understandable. For my part, however, I am used to having two different bodies anyway.

So here is my question to you: Other than the benefit of having some Nikon lenses that Canon does not have yet, what can the D850 (or Z7) do that Canon R5 cannot?

Fair question. I am afraid not everyone is going to like the answer, so I'll again point out that it is my answer, not a universal one. I will answer only for the Nikon Z7 II, the camera I intend to keep, ignoring the D850.

For the first half of my answer, I'll use DPReview as a reference:

https://www.dpreview.com/reviews/buying-guide-best-cameras-for-landscapes

While the AF still lags behind others and disappoints with erratically moving subjects (it works well for subjects with less or steady movement), the overall results my Z7 II produces for landscape shots, for example, are very pleasing. Could the R5 get there or at least get close? DPR liked the Z7 II better, but in any case, I may never even find out.

This is because of the second half of my argument:

What mostly gets overlooked in the DSLR-versus-ML wars, which to me seems to apply to Canon and Nikon alike, is that it is not so much the body but the lens that makes the difference. The wider bayonets, the much closer flange distance, and the fact that lens designs have made substantial improvements over the past 10-15 years or so led to these ML lenses being far superior to older designs. Nikon picked the widest bayonet and closest flange distance, which seems to have helped: their Z lenses are extremely good almost across the board. My second reference is German photo mag ColorFoto, which has been around for 45 or so years and always excelled with diligent, systematic and repeatable lens and body testing that considered only 'hard data', so price, haptics, accessories and the like play no role in their scores.

The average score for the 11 RF lenses they tested so far is 101 points. (I am discounting the 600 and 800 f/11, which each received 81 points and would otherwise pull the average down quite a bit). For comparison, the average EF lens score is below 80 points, evidence for how much better the RF lenses are.

In case of Nikon, however, where the average of the older F-mount lenses is even lower than Canon's EF average, the 14 Z lenses the magazine tested so far scored an average 108 points, the highest of any camera maker. In other words, the RF lenses are very good, but the Z lenses are even better.

So, which incentive do I have to replace the Z7 II and four Z lenses I own now with another R5 and the corresponding RF lenses I would need to buy? For the above reasons, I fail to see a benefit warranting the investment.