Unsurprisingly, the
Canon EOS R vs. 5D Mark IV comparison shows the two cameras about equal with an important note. That note is that the 5D Mark IV's image is slightly sharper. While it immediately looks like the 5D IV is delivering better image quality, that is not necessarily the case.
We have long been using a low
Canon Digital Photo Professional sharpness setting of "1" (on a 1-10 scale) for lens testing as sharpening quickly masks differences between lenses. While it seems that increasing the sharpness of an image is a cheap fix to poor lens quality, that sharpening quickly becomes destructive to details, ruining the fine image quality you were seeking in the first place. Camera manufacturers know that you like sharp images and they crank up the default sharpness in attempt to make you happy. Nearly always, that setting is at a very destructive level. Fortunately, you can adjust the sharpness level to your taste.
There is a long pipeline between the imaging sensor and the final image file and not all cameras utilize identical hardware and software (most often, they do not). More specifically to the point, the amount of sharpening showing in a final JPG image processed using the same settings is not always the same. And, that is the case here.