The replacement unit I received immediately seemed to have a better and brighter display, which is confirmed by the measurements graphs attached.
The replacement is brighter, with warmer white point, its RGB channels curves response are a lot closer across the board.
From comparing two phones, I can't tell if one is just better than the other or if Google improved the factory calibration process.
Neither display's white look like D65 daylight white compared to actual daylight or a reference CRT monitor (regardless of the sensor used).
Maximum brightness – significant difference
original: 409 cd/m², replacement 510 cd/m²
Contrast ratio – about the same
original: 926:1, replacement: 952:1
Average gamma – interestingly about the same despite the difference in curves
original: 2.07, replacement: 2.08
Up next: results calibrated 😉