Drivetrain
The Suzuki SX4's engine is substantially smaller than the Legacy's. Keep in mind that a smaller engine usually has to work a little harder; on the flip side, smaller engines typically get better gas mileage.
The Suzuki SX4 could learn a lesson or two from the Subaru Legacy in terms of torque.
Utility
The Subaru Legacy is a better choice than the Suzuki SX4 regarding hauling capacity, especially if you frequently need to carry a lot of suitcases or big pets.
Neither the Suzuki SX4 nor the Subaru Legacy has a marked advantage as far as seating capacity.
Convenience
You'll quite certainly have to take the Suzuki for a fill-up more often than the Legacy because of its tank size and fuel economy.
Comfort
While the front cabin in the Suzuki offers a bit more head room than the Subaru Legacy, there honestly isn't much of a difference.
The Suzuki SX4 offers more head- and leg-room to your passengers than the Subaru Legacy does.
Dimensions
The Subaru Legacy is markedly heavier than the Suzuki SX4.
Your wallet will hurt more every time you fill up the Subaru Legacy than the Suzuki because of its larger tank.
The Suzuki SX4 fits in smaller parking spaces than the Subaru Legacy.
The Suzuki SX4's shorter wheelbase will likely give a nimbler feel in daily traffic. On the other hand, the Subaru Legacy is likely to have a smoother, more stable ride.
Cost
The destination charge is a standard charge for transporting the vehicle from its point of origin to the dealer. It costs roughly the same to get the Suzuki to the dealership as the Subaru Legacy.
The Legacy won't tax your gasoline budget significantly more than the SX4 will.
The Subaru Legacy doesn't pale in comparison to the Suzuki SX4 in terms of fuel economy.
The Suzuki SX4 is tremendously less costly than the Subaru when it comes to MSRP.
Overview
The Subaru Legacy and the Suzuki SX4 have the same basic warranty.