Utility
Drivers with frequent child-duty might favor the Audi A4 over the Porsche Boxster.
Performance
As far as horsepower, the Porsche Boxster packs quite a wallop and will knock the Audi A4 down a few rungs. However, note that high horsepower engines often command higher insurance premiums.
Dimensions
The Audi is tremendously more bulky than the Boxster.
The Porsche Boxster's tank is almost the same size as the Audi's, though the A4's is slightly larger.
The Porsche Boxster and the Audi compete for the same parking spaces.
The Porsche's shorter wheelbase will likely give a sprier feel in daily traffic. However, the Audi A4 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. The A4 is substantially cheaper to get to the dealership than the Boxster.
The Audi A4 is substantially less expensive than the Porsche Boxster with respect to MSRP.
Drivetrain
The Porsche Boxster has a bigger engine than the Audi A4. Keep in mind that smaller engines typically get better gas mileage, but a smaller engine usually has to work a little harder.
Torque is roughly equivalent to acceleration, and in this respect, the Porsche Boxster isn't much more powerful than the A4.
Comfort
While the front cabin in the Porsche Boxster offers a bit more head room than the Audi A4, there honestly isn't much of a difference.
Warranty
The Audi A4 and the Porsche Boxster have the same basic warranty.