Cost
The destination charge is a standard charge for transporting the vehicle from its point of origin to the dealer. It costs almost the same to get the Dodge Viper to the dealership as the Porsche Cayman.
As far as MSRP, the Dodge Viper costs tremendously more than the Cayman.
Utility
The Viper and the Porsche Cayman can accommodate the same number of passengers.
Dimensions
The Dodge Viper is tremendously more bulky than the Porsche Cayman.
The Dodge's tank is almost the same size as the Porsche's, though the Cayman's is somewhat bigger.
The Porsche Cayman and the Viper compete for the same parking spaces.
Performance
In terms of horsepower, the Dodge Viper packs quite a punch and will knock the Porsche Cayman down a few rungs. On the other hand, bear in mind that high horsepower engines often command higher insurance premiums.
Handling
With its tighter turning circle, the Porsche Cayman is most certainly sprier than the Dodge Viper, something to consider if you do a lot of city driving; however, note that a vehicle with a tight turning circle may feel a bit twitchy on the highway.
Drivetrain
The Porsche Cayman's engine is tremendously smaller than the Dodge Viper's. Note that a smaller engine usually has to work a little harder; on the other hand, smaller engines typically get better gas mileage.
Torque equals pickup, and the Viper will have picked up and gone by the time the Porsche Cayman finally gets moving.
Warranty
The basic after-sale protection that comes with the Dodge Viper isn't quite as generous as the Porsche Cayman's.