Performance
With that kind of horsepower, the Audi is a true speedster.
With respect to horsepower, the Audi S5 packs quite a wallop and will knock the BMW 328 down a few rungs. On the flip side, bear in mind that high horsepower engines often command higher insurance premiums.
Handling
With their comparable turning radii, the BMW 328 and the Audi S5 most definitely handle about the same into and out of tight spots.
Drivetrain
The BMW 328's engine is significantly smaller than the Audi S5's. Bear in mind that smaller engines can be stressed more; however, smaller engines are often cheaper to fix.
The BMW 328 could learn a lesson or two from the Audi when it comes to pickup.
Torque equals pickup, and the Audi S5 will have picked up and gone by the time the BMW finally gets moving.
Utility
Neither the BMW 328 nor the Audi has a marked advantage in terms of seating capacity.
Convenience
The Audi S5's fuel tank will need to be replenished more often than the unit in the BMW.
Comfort
While the front cabin in the Audi S5 offers a bit more head room than the BMW 328, there frankly isn't much of a difference.
Dimensions
The BMW's tank is approximately the same size as the S5's, though the Audi S5's is a little bigger.
The BMW 328 and the Audi S5 compete for the same parking spaces.
Cost
The Audi S5 pales in comparison to the 328 with respect to fuel economy.
The Audi S5 will tax your gasoline budget considerably more than the BMW 328 will.
The Audi S5 is significantly pricier than the 328 with respect to MSRP.
The Audi S5 will cost you a bundle in gasoline every year compared to the BMW 328.
The BMW 328 will save you a bundle at the pump every year compared to the Audi S5.
Warranty
The S5 and the BMW 328 have the same basic warranty.