I can't speak for Tesla's FSD specifically, but Waymo did a study on the collision rate of their autonomous cars compared to human drivers: https://waymo.com/safety/impact/. They found that Waymos get into about 81% fewer crashes per mile. Compared to a statistical human driver, Waymo prevented around 411 collisions that would have resulted in any injury, and 27 collisions that would have resulted in serious injury or death. It seems like for Waymo specifically, self-driving cars are demonstrably safer than human drivers. Not sure if that generalizes to Tesla FSD, though.