Utility
The TT will most definitely prove more practical than the Dodge for those of you with frequent kid-cargo.
Performance
With respect to horsepower, the Dodge packs quite a punch and will knock the Audi TT down a few rungs. However, note that high horsepower engines often command higher insurance premiums.
Dimensions
The TT is a little more ponderous than the Dodge Viper.
The Audi TT's tank is about the same size as the Dodge Viper's, though the Dodge Viper's is a tad larger.
The Dodge Viper rides lower than the Audi TT, which is a good thing for its center of gravity and ease of access.
The TT and the Dodge Viper 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 TT is quite a bit cheaper to get to the dealership than the Viper.
The Dodge Viper is tremendously more expensive than the TT when it comes to MSRP.
The Audi TT will save you a bunch of money at the pump every year compared to the Dodge Viper.
Handling
The Viper has tremendously bigger tires than the Audi TT. Keep in mind that wider tires could improve handling, while smaller tires might improve gas mileage.
With its tighter turning radius, the TT is quite certainly sprier than the Dodge, something to consider if you do a lot of city driving; however, keep in mind that a vehicle with a tight turning circle may feel a bit twitchy on the highway.
Drivetrain
The Audi TT's engine is tremendously smaller than the Dodge Viper's. Keep in mind that smaller engines can be stressed more; on the flip side, smaller engines are often cheaper to fix.
Torque is roughly equivalent to acceleration, and in this respect, the Dodge is tremendously more powerful than the TT.
The Dodge Viper packs quite a wallop compared to the Audi TT in terms of torque, which is the force that lets you accelerate quickly.
Comfort
Taller drivers will markedly enjoy the extra head room in the TT's front cabin compared to the Dodge Viper.
Overview
The basic after-sale protection that comes with the Dodge Viper isn't quite as generous as the TT's.
Other
The Dodge Viper emits fewer smog-forming pollutants per 15,000 miles than the Audi TT.