Handling
With its tighter turning radius, the Mercury Mountaineer is definitely more agile than the Lexus RX 350, something to consider if you do a lot of city driving; however, remember that a vehicle with a tight turning circle may feel a bit twitchy on the highway.
Drivetrain
The Mountaineer's engine is considerably bigger than the Lexus RX 350's. Keep in mind that more massive engines may use more gasoline than smaller ones.
Torque is roughly equivalent to acceleration, and in this respect, the Lexus RX 350 isn't much more powerful than the Mercury.
Utility
The Mercury Mountaineer will quite certainly prove more convenient than the Lexus RX 350 for those of you with frequent kid-cargo.
The Mercury Mountaineer outpulls the Lexus RX 350 by a large margin.
Convenience
The Mercury Mountaineer's fuel tank will need to be replenished a tad more often than the unit in the Lexus RX 350.
Comfort
While the front cabin in the Mercury Mountaineer offers a bit more head room than the RX 350, there really isn't much of a difference.
The Mercury Mountaineer is not particularly more spacious for your passengers than the Lexus RX 350.
Dimensions
Your wallet will hurt more every time you fill up the Mercury Mountaineer than the Lexus RX 350 because of its bigger tank.
The Lexus RX 350 and the Mountaineer 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 almost the same to get the Mercury Mountaineer to the dealership as the Lexus RX 350.
The Mercury will tax your gas budget significantly more than the Lexus RX 350 will.
With respect to gas mileage, the Lexus RX 350 has the Mountaineer beat.
The RX 350 isn't much costlier than the Mountaineer as far as MSRP.
Overview
The basic after-sale protection that comes with the Mercury isn't quite as generous as the Lexus RX 350's.