The always polarizing DXOMark has released their sensor score for the Canon EOS R3, and it's the highest for any Canon camera in their database with a score of 96. While this may be Canon's highest sensor score ever, it's still behind offerings from Panasonic, Sony and Nikon, but very slightly.
DXOMark did call the Canon EOS R3 the best low light performer in their full-frame sensor database, something Canon hasn't been at the top of for quite some time.
While we’ll have to wait and see what form a possible top-of-the-range EOS R1 takes, the Canon EOS R3 is certainly a compelling contender for its intended market. Not only does it have excellent dynamic range at key low, mid and high sensitivities, it has the best low light performance of any full-frame camera in our database. This makes the Canon EOS R3 a very attractive option for Canon EOS-1DX Mark III users transitioning over to Canon’s mirrorless RF system and it’s a solid option for any photographers new to the Canon brand. Read the full review