Utility
The Pontiac and the Saturn Astra can accommodate the same number of passengers.
Convenience
You definitely won't have to visit your friendly gas station more often with the Pontiac Vibe than with the Saturn Astra, because both offer comparable ranges.
Dimensions
The Saturn's tank is approximately the same size as the Vibe's, though the Pontiac Vibe's is a little larger.
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 Saturn Astra to the dealership as the Pontiac Vibe.
The Pontiac uses a lot of gasoline compared to the Saturn Astra.
The Saturn Astra will save you money at the pump compared to the Pontiac Vibe.
With respect to MSRP, the Pontiac Vibe costs almost as much as the Saturn (though the Saturn is a little cheaper).
Warranty
The Saturn Astra and the Pontiac Vibe have the same basic after-sale protection.