Not too sure if the rent a car services return more than Uber as an owner driver
However from my experience of having done Uber driving, realistically the actual earnings, if you account for depreciation of the vehicle as well is just meager - way below minimum wage per hr here
Here the Taxi drivers traditionally use cars like Holden, Toyota etc., that can drive for even 500,000 KMS
Taxi drivers in the past, could make a decent living as there were few of them in a location but Uber I believe turned that balance upside down..
This might sound silly but did you consider why there are cheaper to operate, Three wheelers in countries like SL as Taxis..?