Lets start with the similarites between the two performance crossover SUVs.
The Infiniti FX and the Porsche Cayenne, both came into existance in the year 2003. They act sports cars (they are), seat 5 and doesn't come with hybrid engine option. Some of the features that might be irritating to a car enthusiast like stability control and damping control can be easily switched off. At best both only manage to attain mpg figures that hover around 15 in city and 20 in highway driving.

Alright thats enough of frienship making. Let bring out the daggers and see them head-to-head.

Engine & Power
08 Porsche Cayenne S comes with 4.8-liter V-8 that makes 385 hp at 6200 rpm and 369 lb-ft of torque at 3500 rpm, and uses a six-speed Tiptronic S gearbox. Infiniti FX50's VVEL 5.0-liter V-8 has advantage of five more horses over Cayenne S with 390hp at6,500 and a 369 lb-ft of torque 4,400 rpm.

Transmission
FX50 comes with seven-speed automatic transmission while Cayenne has to work with a six-speed Tiptronic S gearbox.

Performance
Of the two, Cayenne S is not the faster one. Average from various sprint tests performed shows that Infiniti's FX50 wins the 0-60 run with a comfortable margin of more than 1 sec. And this difference further increase in 0-100 race with Porsche's Cayenne S lagging behind by 4.5 seconds.

Gadgets
FX50 being the latest of the two has more electronic gizmos. These include 11-speaker Bose audio, 9.3GB Music Box hard drive and rear-seat DVD system for entertainment. For safety Infinit packed FX50 with ABS with EBD, TPMS (tire pressure monitoring system), AFS (adaptive front lighting system), DCA (distance control assist), IBA (intelligent brake assist), ICC (intelligent cruise control)and LDP (lane departure prevention) along with XM NavTraffic and Around View Monitor that comes with rearview camera and a four-quadrant exterior video monitor.