New images showing the Xiaomi 12 Pro's 50 MP main camera sensor right next to the Google Pixel 4's 12 MP sensor have now surfaced. The difference in sizes is just as much as one would expect, although it's important to point out that bigger isn't always better.
https://www.notebookcheck.net/Xiaomi-12-Pro-and-Google-Pixel-4-camera-sensor-size-comparison-shows-how-far-camera-hardware-has-come.595006.0.html