Ford Fiesta or Toyota Yaris

hello, my mother wants to buy a car for max. 5000 euros. the selection is the fiesta (2001-2008) and the yaris (2nd generation 2005-2011). the car must have an automatic transmission. is it true that a diesel engine with an automatic is better able to cope and the consumption of the car does not increase as much as with the gasoline? which car would you recommend to me in terms of consumption and other costs, such as reperaturability. or is there still alterna I would have thought at the fiesta that with the 68 hp you can drive the car with 130 or 140 on the highway, already at the power limit. I hope you can help me and thank me already in advance.