The CA DMV autonomous vehicle reports of accidents and disconnects are the closest thing available to objective data right now. Waymo is way ahead on disconnects. Cruise is getting rear-ended a lot lately. Google used to get that a lot, but they seem to have gotten past that.

(The main compatibility problem with autonomous vehicles so far is being rear-ended. The typical situation is that the autonomous vehicle advances into an intersection, detects some good reason to stop like cross-traffic previously occluded, stops, and gets rear-ended. The accel/decel profile for entering occluded situations may have to be made more compatible with human behavior to get the human drivers behind to behave properly. This isn't a big problem; damage in those collisions is very low.)