Is there a significant difference between the fuel economy of Toyota Camry 2004-2006 and Corolla 2003-2010?

You won't be driving either of those for Uber, they're too old. In any case, comparing '06 models with the 4 cylinder engines does give you significantly better fuel economy in the Corolla (Camry is heavier and has a bigger engine). The difference is smaller comparing '15 models (Corolla is now 'midsize' instead of 'compact'). But don't forget the harder-to-enumerate factors like comfort and drivability, you're going to be in that thing all day.

just get a corolla. the reason the camry costs more is mainly because of the way it looks. it's supposed to look slightly nicer than a corolla, which allows the manufacturers to jack up the price, even though they both probably cost about the same to make.

Get a Prius or an electric vehicle/hybrid. They save you way more on gas and if you plan to keep the vehicle it’ll pay for itself in the long run.