Utility
The Subaru Forester's bigger trunk will accommodate more massive things than the MAZDA3.
The Mazda MAZDA3 and the Subaru Forester can accommodate the same number of passengers.
Dimensions
The Mazda's tank is approximately the same size as the Subaru Forester's, though the Subaru Forester's is a little more capacious.
The Subaru Forester rides lower than the Mazda MAZDA3, which is a good thing for its center of gravity and ease of access.
The MAZDA3 and the Subaru Forester compete for the same parking spaces.
Convenience
You'll most definitely take the Forester for a fill-up approximately as often as the Mazda MAZDA3.
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 Mazda MAZDA3 to the dealership as the Subaru.
The Subaru Forester won't tax your gas budget substantially more than the MAZDA3 will.
There honestly isn't much of a difference in gas mileage here, but if you must know, the Mazda is a little more economical than the Subaru Forester.
As far as MSRP, the Subaru Forester costs markedly more than the Mazda MAZDA3.
Handling
The Subaru Forester and the Mazda MAZDA3 have about comparable tires.
With their comparable turning circles, the Mazda MAZDA3 and the Subaru Forester likely handle roughly the same into and out of tight spots.
Drivetrain
The Mazda and the Subaru Forester have similar-sized engines, with a slight advantage to the Subaru Forester.
Comfort
While the front cabin in the Mazda MAZDA3 offers a bit more head room than the Forester, there frankly isn't much of a difference.
The ampler interior dimensions of the MAZDA3 make it considerably more spacious for your passengers than the Subaru.
Overview
The basic warranty that comes with the Forester isn't quite as generous as the Mazda MAZDA3's.