Well the corporate culture at Uber is likely the reason why Uber makes claims of background checks, which seem to miss things like felony convictions, and better safety and security than regular taxis, even though when unsafe conditions happen Uber blames the customer rather than trying to accept or fix things.
In other words, Left might be better and safer than Uber not because Lyft has better employees, but because Lyft isn't (necessarily) cutting every possible corner and ignoring everyone's safety and security the way Uber is doing (and always has done).