Handling
With its tighter turning radius, the Porsche is most certainly nimbler than the HUMMER, something to consider if you do a lot of city driving; on the other hand, note that a vehicle with a tight turning circle may feel a bit twitchy on the highway.
Drivetrain
The Cayenne's engine is tremendously smaller than the HUMMER H2 SUV's. Remember that a smaller engine usually has to work a little harder; however, smaller engines are often cheaper to fix.
The Porsche Cayenne could learn a lesson or two from the HUMMER with respect to torque.
Utility
The HUMMER H2 SUV will most certainly prove friendlier than the Porsche Cayenne for those of you with frequent child-cargo.
The HUMMER is a better choice than the Porsche Cayenne in terms of hauling capacity, especially if you often need to carry a lot of luggage or large pets.
There's little the HUMMER H2 SUV can tow that the Porsche cannot.
Comfort
While the front cabin in the HUMMER H2 SUV offers a bit more head room than the Porsche Cayenne, there really isn't much of a difference.
The ampler interior dimensions of the HUMMER make it substantially more spacious for your passengers than the Porsche.
Dimensions
The HUMMER H2 SUV is tremendously heavier than the Porsche Cayenne.
Your wallet will hurt more every time you fill up the HUMMER H2 SUV than the Porsche Cayenne because of its bigger tank.
The Porsche Cayenne and the HUMMER H2 SUV compete for the same parking spaces.
The HUMMER H2 SUV's longer wheelbase will result in a smoother, more stable ride; however, the Cayenne may give a nimbler feel in daily traffic.
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 HUMMER to the dealership as the Porsche Cayenne.
As far as MSRP, the HUMMER H2 SUV costs considerably less than the Porsche Cayenne.
Warranty
The Porsche Cayenne and the HUMMER H2 SUV have the same basic after-sale protection.