Not OP, but both Uber and Lyft tie bonuses to weekly/monthly acceptance rate and rides completed. I can't recall numbers, and they have been tricky to find on my phone. But I too can anecdotally confirm that Lyft drivers seem to enjoy it more in the Bay Area, and one of the reasons I've heard is that the bonus structure is a bit more liberal.
A Lyft driver told me the other day that it was something like a 30% bonus on whatever you had earned that week when you hit 80 rides in a calendar week.