The 6 pro is 0.3" taller and 0.1" wider than the 6. But both are also significantly larger than the previous generation pixels. The Pixel 6 pro for example is 0.8" taller and 0.2" wider than the Pixel 5, which is a significant difference (especially considering you lose the rear fingerprint scanner that gave the ability to swipe down notifications from the unreachable top of the screen).

Camera is different and it's 90hz screen versus 120hz (a deal breaker for me).