Theoretically fixed route service is far more efficient. Practically, it's not because it takes a lot of demand to run at high frequency and high utilization. As an example, I live in Atlanta and it costs the system $9 per bus ride these days. And given the nature of the system and the city it usually takes people more than one bus ride to get where they need to go.
Lyft/Uber usually comes out to be slightly to much cheaper excepting long cross-metro rides. The problem is that I don't get my $15.50 subsidy.