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Mostly because the 8 MP sensor gives better image quality. All else being equal (same sensor generation and such), the sensor with more photosites will better sampling the light, and if viewed at the same output size will give a better image. In low light, it's down to primarily quantum shot noise, which is random, and more sampling of the noise = better.
First-- the two cameras I posted are not really my "finalists" in my search-- more a comparison for my sensor-pixel question. My main goal was to get into a full frame camera, and I was likely going to get a 5D mk iv, but discovered that the traditional DSLR is on borrowed time. I had not looked much at the cameras in several years, and was surprised that Canon (and Nikon) have stopped development of new cameras that are not mirrorless. I decided I better deep dive into the specs and switch to a mirrorless platform since they are a lot more refined than 5 or so years ago when I looked out of curiosity.I mean, they're both fine? Also you're leaving out the Z7 II or Z8 that are in the same market space. The Sony has about a 15% increase in linear resolution above the Canon or Nikon, but in reality you're not going to resolve without jumping through some hoops to get really good glass on it and use perfect technique; and of course the Sony mount is the weakest lens lineup in terms of quality, but the best in terms of depth. Nikon and Canon are about on par for depth of 1st party lenses, Nikon significantly ahead in 3rd party lenses, but current Nikkors outperform the rest of anything in mirrorless significantly. And of course the Z8 exists so you can have your megapixels and speed too, if you want.
The trouble is, you're buying into a camera system. You'll have a new body in a few years if you get into it seriously, but the rest of it will stick around for a while. Go to a local store and see if you can rent each and some lenses for a couple of days and see what works best for you.
Mostly because the 8 MP sensor gives better image quality. All else being equal (same sensor generation and such), the sensor with more photosites will better sampling the light, and if viewed at the same output size will give a better image. In low light, it's down to primarily quantum shot noise, which is random, and more sampling of the noise = better.
The 8 MP camera gives the inferior quality, because of literally everything else that makes up the camera. An 8MP camera should output four times the bitrate, and require at least four times the processing power of a 2 MP camera to realize the gains. There are tricks one can use to bring that down somewhat, but math is math here, and if you target the same bitrate but have four times the pixels, something's got to give, and with MP4 that's always detail that suffers. And that's not even discussing that most security camera lenses are hot garbage and the impacts that has on the image chain. And this is why a competent 8 MP camera costs around 4x as much as an equally competent 2 MP camera and requires 4x the storage.
The Canon R mount has NO 3rd party lenses and of course the Canon's come at a significant premium. I get that you "get what you pay for" in glass. I have two "L" lenses that would cost more than twice as much today as what I paid to replace in a pure R mount. <sigh> I know-- there is an EF converter... I am looking at the R6 Mk ii-- full frame for about $1,000 less than that R5 up there. I am still liking the multitude of lenses available for Sony E-mount though. Sigma Art lenses are excellent-- and at a nice price.Yeah-- it's all stupidly expensive any more. The Canon R6 MkII might be the one.... but we will see...Wow...so out of my league. I just upgraded from a Canon 3Ti to a 8000D and couldn't be happier!
I've actually shot the Sigma Art side by side with the new basic Nikkors, and the Nikkors wipe the floor with Sigma Art in performance. It's been a common theme of late, Nikon moved to a mount that's gigantic and close to the sensor and they're putting out really high quality lenses (they are a very serious optics company, after all), with their plastic kit lenses resolving as well as some of Sony's GM models; Sony's E-mount is the most restrictive, being designed as an APS-C mount, and the lenses suffer, especially in the corners. The R mount sits in between but is much closer to Nikon, but Canon's trouble is they seem to choose compactness over performance in their designs, and never quite had the lens design talent of Nikon.
Yeah-- I have been looking closely at the A7iv (no R)-- but I am definitely leaning more towards the EOS R6 now...