Handling
With its tighter turning radius, the Subaru Forester is definitely more maneuverable than the Mazda MAZDA6, something to consider if you do a lot of city driving; on the other hand, remember that a vehicle with a tight turning circle may feel a bit twitchy on the highway.
Drivetrain
The Subaru's engine is quite a bit smaller than the Mazda MAZDA6's. Note that a smaller engine usually has to work a little harder; however, smaller engines typically get better gas mileage.
The Subaru Forester could learn a lesson or two from the MAZDA6 with respect to pickup.
Utility
Neither the Mazda nor the Subaru Forester has a marked advantage when it comes to seating capacity.
Convenience
You very likely won't have to visit your friendly gas station more often with the Forester than with the Mazda MAZDA6, because both offer similar mileage ranges.
Comfort
While the front cabin in the Subaru Forester offers a bit more head room than the Mazda MAZDA6, there frankly isn't much of a difference.
The Mazda MAZDA6 offers more head- and leg-room to your passengers than the Forester does.
Dimensions
The Forester's tank is about the same size as the Mazda MAZDA6's, though the MAZDA6's is a little more capacious.
The Subaru Forester rides lower than the Mazda MAZDA6, which is a good thing for its center of gravity and ease of access.
The Subaru Forester and the Mazda MAZDA6 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 approximately the same to get the Mazda MAZDA6 to the dealership as the Forester.
The MAZDA6 pales in comparison to the Subaru Forester in terms of fuel economy.
With respect to MSRP, the Subaru costs roughly as much as the Mazda MAZDA6 (though the Mazda MAZDA6 is a tad cheaper).
Overview
The basic after-sale protection that comes with the Subaru Forester isn't quite as generous as the Mazda MAZDA6's.