The Canon EOS R6 is an ideal mirrorless camera for both photographers and video content creators who want a strong and versatile camera to keep up with their active lives, and it is a direct competitor for the Sony a7 III, Nikon Z6 II and Panasonic S5 in the prosumer segment.
Mathieu Gasquet has finished a very exhaustive Canon EOS R6 vs Sony a7 III review, including photography and video. You can see top 10 main differences between the Canon EOS R6 and the Sony a7 III, including sensor and image quality, autofocus, continuous shooting speed, image stabilisation, video, design, viewfinder and LCD, Battery life, Lenses and price.
Conclusion from MirrorlessComparison:
The autofocus system and burst speeds are impressive, and Canon has out-classed Sony in its own territory with features like Animal Detection. The image quality is on par, if not slightly better, albeit with 20% less resolution. The image stabilisation is also superior (although not as much as the official specifications suggest) and I personally prefer the ergonomics, button layout and dials response on the EOS body.
As nice as the R6 sounds, there are some strong points in favour of the A7 III to keep in mind. It may not have 4K/60p or 10-bit internal recording for video, but it doesn’t suffer from overheating as severely as the Canon. There is a plethora of native lenses to choose between for the E-mount system, not just from Sony but also third-party brands, and that also means a better choice of affordable glass. Last but not least, the Sony is less expensive.
You can read the full review at MirrorlessComparison.