I trust statistics but I don't trust bad statistics. There isn't a self driving car operator out there that is currently testing their cars in statistically representative conditions. And unless they are, there isn't a statistical methodology out there that can say they are safer.

Google, for example, avoids expressways and won't go on freeways, hasn't tested their cars in extreme weather, barely ever sees even bad weather, and is electronically limited to 25mph. I'd be willing to bet the majority of drivers have nearly perfect driving records in those conditions too.