SUMMARY
Photographer Alex Barrera compared the Sony a7R VI and a7 V for still image quality, finding that the higher-resolution a7R VI offered better highlight and shadow recovery, and surprisingly cleaner high ISO performance. However, the a7 V produced punchier, more vibrant out-of-camera raw files with preferred skin tones. Barrera concluded that while the a7R VI is a better overall package, image quality alone isn't a sufficient reason to upgrade, especially if the a7 V's color science is preferred for controlled portraits.
TAKEAWAYS
Sony a7R VI offers better highlight/shadow recovery and cleaner high ISO than a7 V.
Sony a7 V's raw files provide punchier colors and preferred skin tones out-of-camera.
Higher resolution doesn't guarantee better image quality; color science can be a deciding factor.
Stacked sensor technology in the a7R VI primarily benefits readout speed, not static image quality.