so lets look at your car. a 1997 Camry is longer by 46 inches, but only taller by 2.8 inches. and the mini is wider by 5.1. so if you look at the specs, the mini will park way easier, stay on the road better, and has a lower center of gravity, making cornering a breeze.
the 2.4 liter (AUTOMATIC!!) camry's gas mileage is 24/34. the mini cooper s (MANUAL!!) is 25/32. but i doubt you can get that much out of the mini when you drive it like it was meant to be. It is very much possible to get under 15 when you have fun. the camry is 500 pounds heavier and has drum brakes in the back. the camry goes from 0-60 in 11.8, the mini in 6.8. end of story.