Performance
As far as horsepower, the Mazda packs quite a wallop and will knock the Scion down a few rungs. However, remember that high horsepower engines often command higher insurance premiums.
Handling
With their comparable turning circles, the Mazda MAZDASPEED3 and the Scion most certainly handle roughly the same into and out of tight spots.
Drivetrain
The Scion xD's engine is considerably smaller than the Mazda MAZDASPEED3's. Note that smaller engines can be stressed more; on the flip side, smaller engines are often cheaper to fix.
The MAZDASPEED3 packs quite a wallop compared to the Scion xD when it comes to torque, which is roughly equivalent to acceleration.
Torque is the force that lets you accelerate quickly, and in this respect, the Mazda MAZDASPEED3 is tremendously more powerful than the Scion xD.
Utility
Neither the Scion xD nor the MAZDASPEED3 has a marked advantage in terms of seating capacity.
Convenience
You quite certainly won't have to visit your friendly gas station more often with the Scion xD than with the Mazda MAZDASPEED3, because both offer similar mileage ranges.
Comfort
The ampler interior dimensions of the Mazda MAZDASPEED3 make it more spacious for your passengers than the Scion xD.
Dimensions
The Mazda MAZDASPEED3 is tremendously more bulky than the Scion xD.
Your wallet will hurt more every time you fill up the MAZDASPEED3 than the Scion because of its larger tank.
The Scion xD fits in smaller parking spaces than the Mazda.
The Scion xD's shorter wheelbase will give a more maneuverable feel in daily traffic. On the flip side, the MAZDASPEED3 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 about the same to get the Scion to the dealership as the Mazda.
The Scion xD will save you money at the pump compared to the Mazda MAZDASPEED3.
As far as MSRP, the Scion xD costs tremendously less than the Mazda.
The xD will save you a lots_of_money at the pump every year compared to the Mazda MAZDASPEED3.
The Mazda MAZDASPEED3 will cost you a bundle in gasoline every year compared to the Scion.
Warranty
The Mazda MAZDASPEED3 and the Scion xD have the same basic warranty.