All the changes are mainly in the structure and design of the two cars.

But the motor set up has the same 3.5 liter v-6
its 17/24mpg

Just think of it as two big xbs and xas

the edge has a much more slick smooth look than the edge
and the flex has the boxy look

So i guess you could say the biggest diff.s are the body, chassy, and suspension

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EDIT: also the ford flex is a crossover not a SUV