Performance
The Pontiac is likely to feel slightly sluggish because of its high horsepower-to-weight ratio.
Regarding horsepower, the Mazda packs quite a punch and will knock the Pontiac Vibe down a few rungs. However, note that high horsepower engines often command higher insurance premiums.
Handling
With their comparable turning radiuses, the Mazda MAZDA3 and the Vibe most definitely handle about the same into and out of tight spots.
Drivetrain
The Pontiac Vibe's engine is substantially smaller than the Mazda MAZDA3's. Note that a smaller engine usually has to work a little harder; however, smaller engines are often cheaper to fix.
The Pontiac Vibe could learn a lesson or two from the Mazda MAZDA3 as far as pickup.
Torque equals pickup, and the Mazda will have picked up and gone by the time the Vibe finally gets moving.
Utility
The Pontiac Vibe is likely a better choice than the Mazda MAZDA3 in terms of hauling capacity, especially if you often need to carry a lot of cargo or big beasts.
Neither the MAZDA3 nor the Pontiac has a marked advantage as far as seating capacity.
Convenience
The Pontiac Vibe's fuel tank will need to be replenished slightly more often than the unit in the Mazda.
Comfort
Taller drivers will significantly enjoy the extra head room in the Pontiac Vibe's front cabin compared to the Mazda MAZDA3.
The Vibe is not particularly more spacious for your passengers than the Mazda.
Dimensions
The Pontiac Vibe is likely to feel slightly sluggish because of its high horsepower-to-weight ratio.
The Pontiac Vibe's tank is roughly the same size as the Mazda MAZDA3's, though the MAZDA3's is slightly larger.
The Pontiac and the Mazda compete for the same parking spaces.
Cost
The Pontiac Vibe won't save you much money at the pump compared to the Mazda.
The Mazda MAZDA3 isn't much less costly than the Pontiac as far as MSRP.
Overview
The basic after-sale protection that comes with the Pontiac Vibe isn't quite as generous as the Mazda's.
Other
The Mazda emits fewer smog-forming pollutants per 15,000 miles than the Vibe.