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I actually do not see this as significantly better than the R3. Sure, there are some nice features here. But, if DPR is correct, and it is 2 seconds of shooting full RAW before the buffer fills, that is a significant win for the R3. The R3 is also lighter, it has a mechanical shutter, 30 FPS in full 14 bit RAW (Z9 dropped to a compressed RAW, according to DPR). ... Then we get into performance of AF, AF modes, etc, where I'll want to see production models compared before commenting.
Not wanting to get into a spec war, just saying, depending on how things play out, I can absolutely see where the R3 not only holds its own but may even be better than the Z9 in certain scenarios and for certain people. I think it is great for Nikon users, you have a good tool at your disposal, but my world with Canon is doing just fine as well.