Was out shooting Smew with a fellow birder who shot a Canon crop body with the 100-400II lens. The light changed and he stopped shooting because he felt the shots would no longer be worth it, and I had to agree with him based on my own 7DII. But as I now had the Nikon D500, I still went on for a bit before we went off to search for a few goldfinches.
Not meaning to speak ill of Canon, it's much more nuanced than that, and what a lens that 400DOII is, but the 7DII is just só long overdue for replacement (sensor wise) that it gives me freedom to have the Nikon D500 around for the coming years until Canon finally works out what to do about the 7DII replacement

The main issue is that the 7DII cannot handle difficult light, and you are forced to always search for optimal light, which I ultimately found too much off a constraint on my freedom to go out shooting when I feel like it, instead of only when the light is perfect. With the Nikon D500, I now have back the freedom to work on the images in post. There is much more to say about how the combo's compare, but for now I am not ready to "dump" my Canon set yet, and besides, the people on this thread have gone through it all before me anyhow...

What a beautiful species. I had to google Smew, as I'd never heard of it. I can see where they could be a challenging capture with the white / black contrast. Very nicely captured here.
I can relate 100% to what you're experiencing in contrasting the D500 & 7DII. Honestly, It's just one of those situations where a person really has to experience both in order to truly appreciate the difference. The best way being starting with the 7DII & becoming comfortable with it 1st. I can say that, because I shot one from the time they were released until I switched in late 2018.
The following Hermit Thrush, while not great, would not have been possible with the 7DII.

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