I have a 172. Awesome cars. The Clio is more fun and chuckable where as the megane is faster and more refined.
Mpg on the meg will be comparable to or worse than the 350z I've heard but will be better for long mile munching than the clio. The meg with a remap will be very quick where as the Clio is fast enough to have fun but will be obviously slower than the meg.
Clio is 3 door also which might make things hard?