Big, brawny V8s, screaming tires and high-speed circuit driving. No, it's not a supercar showdown - it' SUV comparison? In the case of these two rather extraordinary SUVs, that's precisely what's on offer. Ride along with the gang at Fifth Gear as they test the two mega-SUVs back-to-back on the course at Anglesey.

While both feature 4.8L V8s at their core, the Porsche extracts 55hp more from the engine, and it offers a sportier suspension and braking package. On the other hand, the X5 weighs nearly 200lbs less. Which will emerge the winner? Watch and find out.