- yes, there is no a9 competitor, correct and I agree that this is an issue if you only shoot Nikon with mirrorless bodies
- the discussion around the lack of dual slot on the Nikon has internet still shaking, it was discussed at nauseum, probably more than any other spec aspect in a camera before. This is a problem and I would far prefer them to have 2 slots even if XQD is indeed the most reliable memory card format ever
- the Sony a7riii AF is superior, but the Z7 AF is no slouch either, in particular since firmware 2.0
- the aspects I find superior on the Nikon are: the mount and its long time promise in terms of lenses, the colors I find more pleasant (call it subjective it you like), the EVF experience, ergonomics (including but not only menus), weather sealing, possibility to adapt any lens (including Sony FE lenses), thinner sensor glass (good for glass adaption), ISO 64, auto-ISO implementation
Cheers,
Bernard