I was in SF a few weekend ago and rode both Waymo and normal Lyft style taxi cars. the Waymo was a better experience in every single way. One of the Lyfts i was in drove on the shoulder for a while like it was a lane. The Waymos were just smooth consistent driving. No aggressive driving to get you dumped off so they can get to the next fair.
So it might come down to how many "9s" you're comfortable with. The experience is really good 99.999% of the time until it's not, and that "not" could be catastrophic. I suppose the data engineers are quite confident in the 9s.
Waymo is 100% with zero fatalities.
But then again, the Concorde was the safest airplane ever built for nearly 30 years, until its first crash and then it was the most dangerous passenger jet ever with 12.5 fatal events per million flights.[1]
Lies, damned lies, and statistics.[2]
0: https://assets.ctfassets.net/vz6nkkbc6q75/3yrO0aP4mPfTTvyaUZ...
1: https://www.airsafe.com/journal/issue14.htm
2: https://en.wikipedia.org/wiki/Lies,_damned_lies,_and_statist...