Handling
With its tighter turning circle, the Mercury Mountaineer is definitely sprier than the Ford Flex, something to consider if you do a lot of city driving; however, note that a vehicle with a tight turning circle may feel a bit twitchy on the highway.
Drivetrain
The Mercury Mountaineer's engine is considerably larger than the Ford Flex's. Note that more massive engines may use more gasoline than smaller ones.
The Ford Flex has no lessons to learn when it comes to torque from the Mercury Mountaineer.
Torque is roughly equivalent to acceleration, and in this respect, the Mercury Mountaineer isn't much more powerful than the Ford Flex.
Utility
Neither the Mountaineer nor the Ford Flex has a marked advantage regarding seating capacity.
Towing is considerably more the Mercury Mountaineer's forte than it is the Ford Flex's.
Convenience
You'll quite certainly take the Ford Flex for a fill-up roughly as often as the Mountaineer.
Comfort
Taller drivers will significantly enjoy the extra head room in the Ford's front cabin compared to the Mercury.
The ampler interior dimensions of the Ford Flex make it roomier for your passengers than the Mercury Mountaineer.
Dimensions
Your wallet will hurt more every time you fill up the Mountaineer than the Ford Flex because of its larger tank.
The Mercury Mountaineer and the Ford compete for the same parking spaces.
Cost
The destination charge is a standard charge for transporting the vehicle from its point of origin to the dealer. It costs about the same to get the Ford Flex to the dealership as the Mercury Mountaineer.
Producing a precise fuel economy evaluation is so tricky that some think not even the federal government can do it, but it looks as though the Ford Flex is the winner as far as fuel economy.
Regarding fuel economy, the Ford Flex is somewhat better than the Mercury Mountaineer, but not by much.
The Mountaineer isn't much less pricey than the Flex in terms of MSRP.
Warranty
The Ford Flex and the Mercury Mountaineer have the same basic after-sale protection.