Cost
The Ford doesn't pale in comparison to the Mercury in terms of fuel economy.
The Mercury Mountaineer won't save you much money at the pump compared to the Ford.
The Explorer isn't much pricier than the Mountaineer regarding MSRP.
Utility
The Ford Explorer and the Mercury can accommodate the same number of passengers.
The Mercury Mountaineer outpulls the Ford by a sizeable margin.
Convenience
You'll definitely take the Ford for a fill-up about as often as the Mercury Mountaineer.
Warranty
The Mercury and the Explorer have the same basic after-sale protection.