Aside from their six-figure price tags, no two cars could be more different than the new 2008 Audi R8 and the 2007 Porsche 911 Turbo. And yet here we are at the drag strip of the Las Vegas Motor Speedway with a shiny, new example of each. We've got five hours to find out if the new midengine, V8-powered Audi R8 supercar can dethrone the legendary Porsche 911 Turbo, the car that has ruled the world of the daily-driven supercar since the mid-1970s.

With only hours with the cars in the same place at the same time, we couldn't hope to work through our usual protocol of test procedures. But getting the 2008 Audi R8 and the 2007 Porsche 911 Turbo together helped provide perspective. We're calling this a guerilla comparison test, and both cars have come loaded for bear.

Like anything that trades in fantasy, the 2008 Audi R8 invites you to dream about speed and style. It's a showcase of modern automotive technology: 420-horsepower V8 with direct fuel injection; all-wheel drive; an elaborate space frame made from aluminum; and leading-edge aerodynamics. It sums up everything Audi knows about the automobile, and yet it's different from any Audi we've ever driven. It's sure to be the top lust-object of the moment when it debuts in the U.S. this fall.

Whether you're looking for a quick, sweaty fling or a lifelong partnership, the Porsche 911 Turbo can be all you imagine. It's an automotive marvel of enduring appeal, and the kind of fantasy car the Audi R8 will be measured against. In its latest form with all-wheel drive and 480 hp, the Turbo is also blindingly fast, beautifully made and easy to live with.

Let the bullets fly.

Our wandering eye
Like the Porsche 911 Turbo, the Audi R8 exterior has a few wild details, yet it appears to be about function, not just form. Exterior designer Frank Lamberty has created subtly chiseled body lines that have an elegant restraint to them, while a unique "sideblade" accentuates the engine's location in the middle of the car.

The Audi designers did, however, let themselves loose with the R8's lighting. Each of the standard bi-xenon headlights is surrounded by 12 LED lights that shine day and night, and LEDs also create a three-dimensional effect for the taillights. Even the glass-enclosed engine compartment lights from within.

Audi was the first car company to get serious about the aluminum chassis and the R8 takes the art to a new level. Extruded aluminum sections are attached with complex castings, then reinforced with aluminum panels. The 463-pound structure is assembled with 325 feet of welded seams, 782 punch rivets and 308 self-tapping screws.

At the business end
The R8's 90-degree, 4,163cc Audi V8 is familiar, but now equal-length intake runners feed the twin throttle bodies, and direct fuel injection helps make possible a 12.5:1 compression ratio. Dry-sump lubrication enables the engine to be located low in the chassis.

The bottom line is 420 hp at 7,800 rpm, and the engine won't quit spinning until 8,250 rpm. Some 317 pound-feet of torque is available between 4,500 and 6,000 rpm, and 90 percent of peak torque is achieved between 3,500 rpm and 7,500 rpm.

Meanwhile, Audi's Quattro all-wheel-drive system distributes as much as 35 percent of power to the front wheels depending on conditions, but the default setting is 10 percent.

Also packing all-wheel drive, the turbocharged Porsche is powered by a smaller 3.6-liter flat-6, but it's the more powerful beast with 480 hp and 460 lb-ft of torque.

Inside story
Although it has just two seats, the Audi's 104.3 inches wheelbase is much longer than the Porsche's, which measures only 92.5 inches. And it's that long wheelbase that gives the Audi a measure of practicality that rivals the Porsche, because the cockpit affords enough leg- and headroom for even big drivers. The 911's rear seat is too tight to really be considered an asset, but a third can ride along if the passenger and the ride are short.

The R8 has a cockpit-style design theme that Audi calls monoposto, an arc of controls that wraps around the driver in the style of a single-seat racing car. In the Audi fashion, the instruments are notable for their clarity and the controls are ergonomically correct. With the fussy little buttons of the Porsche 911 Turbo for contrast, it's easy to appreciate the R8's systematic layout.

Reflecting modern design and processes, the R8 feels good everywhere you touch it. The tall, wraparound seats provide a secure embrace. The steering wheel has a core of lightweight magnesium, yet it is wrapped in soft leather, and the flat-bottom design makes it easy to climb in and out of the car.

Like a Porsche, the R8 has a dimension of practicality, with long doors for easy ingress and egress, storage cubbies and even cupholders. There's a storage shelf behind the seats that will even accommodate two golf bags.

Taking the wheel
There's nothing like the push in the back that the Porsche's turbocharged flat-6 gives you, as if you were surfing an enormous wave. The Turbo also has a wonderfully elastic band of power, with peak torque available from 1,950-5,000 rpm.

The Audi V8's 420 horses arrive at a stratospheric 7,800 rpm, and the engine leaves behind a ripping exhaust note, like a NASCAR V8 that's been to charm school. Surprisingly, this engine also delivers 90 percent of its peak torque from 3,500-7,500 rpm, so there's a power band wide enough to back up the statement of authority made high in the rpm range.

The R8's transaxle might make you love the Audi V8 even more — or it might not, depending. The standard six-speed manual gearbox works great, as the short lever on the center console operates smoothly and with little effort. The optional R tronic transmission is the glamorous choice — an automated, sequential gearbox with a refined single-clutch design (completely different in concept than the twin-clutch Audi DSG). It has both a "Sport" and "Normal" shift mode, and our R tronic-equipped test car confirmed that the gearchanges are swifter and smoother than those we've experienced in similar transmissions from Aston Martin, BMW and Ferrari.

Yet we have mixed feelings about the R tronic. Like so many similar designs, it can work great, if what you're asking of it precisely matches its programming. At full chat on a racetrack, it's lovely, cracking off quick upshifts and nicely rev-matched downshifts with just a wiggle of a finger on the shift paddles located on the steering wheel. Yet in daily traffic, the R tronic is less perfect, either taking a few beats too long to give you what you ask, or even just doing the wrong thing.

The R tronic doesn't suck the life out of the R8, but it's not ideal. Unless we were planning a lot of track days for the R8, we'd be old-fashioned and jam our own gears.

Getting down to business
Once you get after it, the R8 feels stuck down hard to the ground yet delightfully willing to change direction. Even when you leave the stability system engaged, you feel a faint tickle of risk, and the tail of the car leans out just a bit as you flail around a track. Reduce the stability system's intervention by selecting Sport mode or shut off the system entirely, and you get to play the hang-it-out hero all by yourself. The R8 is plenty lively in that mode, but still not twitchy or evil or unpredictable.

As we squeezed out all the Audi had to give on the skid pad and slalom course, the R8 felt marginally more capable than the 911 Turbo and, more important, much more user-friendly around the limit. After his turn at the wheel, Senior Road Test Editor Josh Jacquot noted, "In the Porsche, the limit of grip and the limit of control arrive about the same time, but the Audi lets you step over the line and then pull it back."

When you get right down to the numbers, the Porsche's 0.92g skid-pad performance and 68.3-mph slalom speed were trumped by the Audi's 0.96g and 69.2 mph.

In a straight line, though, the Turbo, which was equipped with the five-speed Tiptronic automatic transmission, would not be denied. It catapulted to 60 mph in just 3.4 seconds, making the R8's otherwise excellent time of 4.4 seconds seem glacial in comparison. In the quarter-mile, the R tronic-equipped R8 made the run in 12.8 seconds at 110.2 mph, but the 911 Turbo proved to be untouchable, with a run in 11.6 seconds at 118.5 mph.

When it comes to braking performance, the Audi R8 puts up a strong number thanks to weight distribution and wide tires, plus strong brakes with eight-piston front calipers rubbing on 15.0-inch rotors. Yet the 3,572-pound Porsche 911 Turbo stops fractionally shorter from 60 mph, coming to a halt in 103 feet while the 3,450-pound Audi stops in 115 feet.

The big picture
When you look at the bottom line, we're expecting the Audi R8 to come in at a starting price of $120,000. The Porsche 911 Turbo's base price is $123,695.

Once we completed all of our rating, measuring and testing, the Porsche eked out a narrow victory over the R8. Its crushing advantage in acceleration as well as a few unique features made the difference. Yet we never felt the Audi R8 suffered in the comparison. In fact, the Audi R8 makes the Porsche 911 Turbo feel old.

With good reason, you will have to grant us. The Audi designers have stretched a taut arresting shape over a lightweight, rigid aluminum frame. They've taken a normally aspirated V8 engine and delivered a lusty output, good flexibility and lovely noises. They've also placed the engine where it belongs in a sports car — behind the driver in the middle of the car. And the combination of a long wheelbase and a carefully refined chassis delivers a finely calibrated balance between great handling and a comfortable ride. And the whole package — especially the cabin — shows a sure sense of style, craftsmanship and quality.

When you're at the wheel of the Audi R8, its easy, controllable poise imparts the sense that the most modern, refined technology has been harnessed to make this a genuine road-going sports car. As fast and thrilling as it can be, this is also an exceedingly comfortable and friendly automobile for daily commuting and long-distance touring. You might want to put the similarly flexible Porsche 911 Turbo in this class, but the Audi still feels more sophisticated and more capable.

The R8 successfully extends Audi's model line beyond coupes and sedans into the realm of the pure fantasy machine. The fact that this car makes you dream about a long-term commitment just makes the whole fantasy that much more enticing.