NEW Nikon Z5: Better than a Sony a7 III, Canon RP or Z6?

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The Nikon Z5 (sdp.io/z5) is Nikon's first mirrorless camera with 2 SD card slots! In my opinion, that makes it the first mirrorless camera really ready to take on professional work, and the first contender against the might Sony a7 III (sdp.io/a73). It has 24 megapixels, FHD @ 60 FPS or 4k @ 30 FPS with a 1.7X crop. It only shoots 4.5 frames per second, which is good enough for portraits and weddings, but probably eliminates it from all but the most casual sports and wildlife photography.
I also compare it against the Canon EOS RP (sdp.io/RP), a $900 full-frame camera that is similar in many ways but lacks the dual memory card slots. The most likely competitors are the Nikon Z6 (sdp.io/z6), which has a similar price, but is now a couple of years old and also only has a single card slot. Finally, I recommend many users consider a used Nikon D750 (about $750 at sdp.io/d750) because it offers similar image quality and dual card slots at a much lower price - but it lacks mirrorless capabilities like Nikon Z-lens support and eye-detect autofocus.