Handling
With their comparable turning radii, the TTS and the Porsche Boxster most definitely handle approximately the same into and out of tight spots.
Drivetrain
The Porsche has a larger engine than the TTS. Remember that smaller engines typically get better gas mileage, but smaller engines can be stressed more.
The Porsche could learn a lesson or two from the Audi TTS in terms of pickup.
Utility
Neither the Porsche nor the Audi has a marked advantage when it comes to seating capacity.
Comfort
While the front cabin in the Audi TTS offers a bit more head room than the Porsche Boxster, there honestly isn't much of a difference.
Dimensions
The Audi TTS is tremendously more bulky than the Porsche Boxster.
The TTS's tank is approximately the same size as the Porsche Boxster's, though the Porsche Boxster's is a bit larger.
The Audi TTS and the Boxster compete for the same parking spaces.
Cost
The destination charge is a standard charge for transporting the vehicle from its point of origin to the dealer. The Audi is considerably cheaper to get to the dealership than the Porsche Boxster.
As far as MSRP, the Audi TTS costs considerably less than the Porsche Boxster.
Warranty
The Audi TTS and the Porsche have the same basic warranty.