While I am still learning the Sony A1 what I notice on the pro side is of course the speed and accuracy of the AF system. I also think the customization options are a bit superior to the Nikon D850 likely on a par with the D6 although I am still plodding up the learning curve. I am also impressed with the color rendering which is on a par with the superb D850. One obvious issue is file volume - at 30 FPS one has a ton to choose from and has been mentioned on this thread the weight of that number is daunting to go through in LR - too much good stuff! On the con side, I note that one has to push the SS up to much higher levels than the D850 (3500 to 4000 +) to capture BIF. The resulting high ISO appears (remember I am coming up the curve) to be noticeably worse than the D850 which is able to do a great job at far less (~2-2.5k) SS and absorb the noise better (to my eye). Now of course, I am typically shooting the Nikon at f/5.6 (500mm f/4 +1.4TC) so I have greater reach and lower ISO for a start - like a stop at least - so therein may lie the story. All that said, the Sony A1 noise is in no way obnoxious and the trade between AF agility, FPS, bird AF, weight, size, versus the D850 combo above is worth it. Not sure I like the Sony for low light however the reviews are quite positive in that regard. Finally, if the Nikon team can make the Z9 20 fps (not certain 30 FPS is a deal breaker for 99% of action photographers) , competing AF to the A1, D6 like customization, 4k video (plenty for next few years) EVF with 240hz update like the A1 they will have gained most if not all of the lost ground. Finally, they have to leverage the Nikon advantage in lens - design interoperability with the greatest number of new and old lens possible - after all, investment in the Nikon lens ecosystem is what's making most of us stay with Nikon as the switching costs are simply too high. What the A1 achieves is a MUCH higher keeper rate than the D850 for action shots, especially birds in flight, that despite my love for the Nikon system has made my mind up about adding it to my bag. If the Z9 comes at or close to the performance envelop of the A1 then back to all Nikon I go.