A Mondeo is more of a "large family saloon" than a medium sized one. I'd say a Focus is more medium sized, where as the Fiesta is a small hatchback. It's down to people's tastes. Just because they can drive a bigger car doesn't mean they want to
I agree, it doesn't take long to get used to them. When I changed from my Cinquecento to my Megane (huge in comparison) I took it out to get some petrol. It was dark, cold and wet. When I got home I felt right at home... So to speak