At one point in this test, I just floored it. I had one of my many lackeys in one vehicle and me in the other. We looked at each other and decided to hammer the suckers on our handy wide-open airstrip. Granted, this was highly informal and not monitored or timed by the hundreds of sanctioning bodies that sanction these things, but the Cayenne Turbo and ML 63 stayed exactly together for at least the first ten or so seconds of tarmac despite those 0-60-mph estimates. Then the Porsche and all 516 lb-ft of its torque from 2250 to 4500 rpm pulled away bit by bit, aided by the lower weight.

Normal top speed for the ML 63 is the Daimler rule of 155 mph, while normal for the new Cayenne (bi-)Turbo hits 173 mph. Then in the curves and through the gears, it became pretty apparent that Porsche has done its homework and at least made the new Cayenne more of a Porsche-style SUV than the previous SUV-style Porsche. The AMG Speedshift 7G-Tronic with selectable Sport-Comfort-Manual knob on the console of the ML 63 is fantastic tech and Mercedes will probably only get an eight-speed to stay "with it" in marketing terms or to have better highway fuel mileage figures. In functional terms, however, seven is enough and the Speedshift box is plenty fast for this thundering hippo.

And there really is thunder going on through the ML 63's four-tip chromed exhaust barrels. Left in Sport, the automatic revs out to about 7250 rpm within the red zone and it's one helluva show. I've got to say, too, that the 15.5-inch diameter AMG steering wheel is mega-sensational for grab positions and thickness. This is one that I muscled around and she appreciates it right back at me.

Clearly the Porsche Cayenne Turbo has a few advantages here that all stem from it being the incoming new kid. Whereas the ML 63 still has the old foot-pedal parking brake and plastic pull release handle ("ka-THUNK"), a standard manual rear hatch that is really heavy, and no onboard reverse camera (at least in my tester), the Cayenne Turbo comes loaded for bear with the space-saving and simple electronic handbrake, automated rear hatch, and reverse camera with a bigger screen. The ML 63 couldn't hide those crow's feet and she became despondent.

But-and every car has a big but-why on earth the Cayenne Turbo comes standard with the old unpleasant Tiptronic S multi-dysfunction steering wheel and thumb-knuckle toggle switches is something I cannot explain. These shift switches quite frankly stink and have been stinking up the place for years. And now that the big Cayenne has the flash new 8-speed Tiptronic S tranny, I comprehend this situation even less. At this level of price ($104,800 plus all your taxes), shouldn't Porsche throw in the much better optional paddle-shifter wheel for free? C'mon. At a base pre-tax price of $91,050 on the ML 63 AMG, it makes the choice here less easy, too.

Both the ML 63 and Cayenne Turbo can be pretty serious off-roaders, but why? Porsche has picked up on this by mimicking a bit what sister vehicle VW Touareg has done, bringing the Cayenne down from the hardcore offroad aspirant and making it much more a real road-goer. The ML 63 has pretty much always been this way anyway and was just waiting for the Cayenne to come join it. The reliable 4Matic setup with 40/60 torque split on the ML63 is as fine a setup as we recall, though the 21-inch in-your-face Pirelli P Zero Rosso tires of my tester must never touch dust or bumps if you wish to stay in love with your purchase. And though the Cayenne Turbo was dressed up, too, in 20-inch Michelin Latitude Sport treads, the active Porsche Traction Management all-wheel drive system is, like the 4Matic, as capable as ever. The Cayenne does benefit now from rear-axle torque vectoring Plus (consists of a large leather-covered cinder block in the cargo floor-yes, seriously, and worth every penny, she is) during dynamics testing, however, and this gives it the edge in chassis trickery.

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