Hunger for more power and torque is insatiable, despite ever-increasing traffic densities and speed restrictions around the world. At least, that's the message relayed by the German auto industry, which continues to up the ante at a breathtaking pace. Just look at the 469-hp Mercedes-Benz CLS55 AMG and the 500-hp BMW M6-which are themselves merely starting points for more developments in this insane race. In the next two years, BMW will introduce a lightweight M6 CSL with about 550 hp and an even more powerful M6 GTR track special. Over at AMG, look for a 503-hp CLS63 AMG and a positively steroidal, 621-hp CLS65 AMG.
There is certainly no shortage of polarizing extremes between the CLS55 AMG and the M6: manu-matic or sequential-manual transmission; high torque or high revs; optimized ride or maximum grip; perfect balance or ultimate involvement; pragmatic beauty or focused fashion; and, of course, supercharged V-8 or normally aspirated V-10. In a way, these approaches sum up the divergent paths that BMW's M Division and Mercedes-Benz's AMG in-house tuner have always taken. These cars aren't as extreme as the AMG Hammer and the race-tuned E30-series BMW M3, but one is a tuned production car, the other more like a detuned racer.
Both cars look terrific. BMW's Chris Bangle has given the M6 its share of flaming surfaces, the nostrils of a race car, and a trunk lid reminiscent of an aircraft carrier's launch pad. Very moderne. M-B's Peter Pfeiffer created a wow-effect crossbreed of a coupe and a sedan, suitably beefed up with aerodynamic add-ons for the AMG version.
On the winding mountain roads of the Austrian Tyrol region, it's all too easy to dismiss the top-of-the-line CLS. Compared with the tied-down and precise M6, the laissez-faire Mercedes feels as if it were shod with winter tires. Even with the air suspension locked in the firmest setting, there is an occasional waterbed wobbliness when pushed. But on the entertainment scale, the arc-shaped four-seater easily matches its rival for lurid drift angles, mid-corner smoke signals, and tire howls that are sufficiently vocal to be registered across the border in Italy or Bavaria. With the traction control deactivated, the haute-couture Benz loves to show off. Since there is a fair amount of mass involved, you don't have to corner at cannonball speeds to trigger the action. In a way, the CLS55 is Germany's twenty-first-century answer to the Buick Grand National GNX: not particularly subtle, but a riot for the driver, the passengers, and the audience.
Whereas the CLS55 AMG takes the smart, casual approach to inspired motoring, the M6 refuses to leave its garage without racing coveralls, helmet, and gloves. The BMW is far less happy to trifle with traffic; it prefers to play at a level where more velocity and more skill are at stake. The grippy chassis hangs on much longer, the tires still carving where the Mercedes has long since resorted to stem turns. The stability control permits a higher degree of slip and slide, knowing that the suspension and steering possess enough skill and sensitivity to avoid drama.
Beyond the tree line, where the cows outnumber the cops, the BMW again emerges as the sharper driving instrument. Unlike the CLS, which retains a conservative electronic safety net even when traction control has been switched off, the 6-series is willing to all but drop its electronic guard. In principle, both cars are gifted playthings, but the M6 is more talented and quite a bit more challenging. It tends to need more space because its front wheels like to run wide before the rear end lets go. This is less of an issue on the track than on the road, where the two-door coupe responds nervously to variations of grip and contour.
The BMW is the better driver's car, a title that is clinched by fabulous steering. Fairly meaty and fluent and full of feedback, it needs just 2.4 turns from lock to lock while remaining linear, regardless of vehicle speed. The drilled disc brakes are equally reassuring. They may be noisy at times, but their performance is almost surreal, with enough power to teach your neck muscles a lesson or two. There are some dislikes-notably ride quality only a fakir would enjoy and high tire, wind, and engine noise.
Softer and less radical in the way it deploys its energies, the CLS55 AMG is a paragon of subtle efficiency. The steering may be less direct and lighter but is hardly short of road feel and on-time response. The brakes have a softer pedal but almost the same stopping power. The bigger barge handles a little more ponderously, but it still goes exactly where you point it, graciously defying its extra size and weight.
Where the Mercedes starship scores is on comfort. Real sports cars don't have to be fitted with torture-chamber seats and crash-bang-wallop suspensions. The CLS has rear seats that can actually accommodate human beings, along with bigger and more adjustable (but not more supportive) front chairs, a quieter cabin, and a much more compliant chassis. Despite its ground-hugging stance, the Mercedes rarely underestimates the depth of a rut or the viciousness of a manhole cover. As a result, it feels more relaxed and composed.
Tech-savvy kids may love iDrive and the seemingly endless modes you can dial into the M6's electronic brain, but very few of them can afford this car, which is aimed at forty-five-year-old-plus affluent males. The clientele's programming skills probably don't reach far beyond the M button on the steering wheel, yet you have to program the settings for it via iDrive. Then you can instantly summon your favorite setup-like P500 (for all 500 horses instead of only 394), M Dynamic (between DSC on and off), the desired shift speed, and the stiffness of the electronic dampers. In M mode, the standard head-up display is activated, depicting gear position, digital road speed, and analog engine speed. Theoretically, you can push the lever into D and let the chips sort out the gearchanges, but that's dreadfully slow and coarse. Best leave it in S and use your index finger to click higher or lower ratios. In the most eager setup, the wizard transmission will shift up in a matter of milliseconds, and it will automatically blip the throttle before switching cogs.
On any demanding stretch of country road, the BMW's sequential transmission is both intuitive and inspiring. In everyday driving conditions, however, its performance is questionable. The predetermined mix of shift speed and throttle response is wrong more often than it's right, and the automatic setting is still too abrupt for day-to-day driving. That's exactly why BMW is preparing a conventional manual gearbox for the American market.
Those who don't care about swapping gears should consider the CLS55 AMG. Its five-speed manu-matic comes with steering-wheel-mounted shift buttons, but the black box is actually so sensitive, smooth, and slick that you can give your digits a rest. A quick learner, the electronic brain adjusts promptly to individual driving styles and preferred patterns. As long as you don't mind the mileage penalty, you can pull the lever down to S and leave it there.
On the autobahn between Garmisch and Munich, it doesn't really matter whether there is a V-8 or a V-10 in charge of propulsion. Maximum speed of both cars is a governed 155 mph, and the 0-to-60-mph acceleration time differs by a token tenth of a second (4.5 seconds for the Merc, 4.4 for the BMW). Although the M6 may be a tad quicker between 100 and 150 mph, any advantage is soon neutralized by traffic. On the secondary country lanes that take us toward Salzburg, however, the different characters of the two engines lead to different rhythms and driving styles.
The 5.0-liter BMW unit doesn't need to be revved hard to keep up with normal traffic, and yet it needs to be pushed to its 8000-rpm redline to stay on the tail of the hard-charging CLS55. Wringing out the 40-valve engine yields extra power rather than extra torque. The V-10 feels most comfortable between 4000 and 7000 rpm, above and below which there's a certain shortage of twist action. The 384 lb-ft muscle mountain peaks at a tall 6100 rpm, entailing the seven speeds that keep your fingers busy.
The supercharged, big-bore Mercedes-Benz engine is a totally different animal. Not only does it dish up a whopping 517 lb-ft of torque-a third more than its competitor-it also serves the energy shock at a leisurely 2650 rpm. Red-flagged at 6500 rpm, the 5.4-liter V-8 delivers its 469 hp at a relatively relaxed 6100 rpm. Five ratios are more than adequate to distribute force that's impressive enough to intimidate the transmission, the differential, the driveshafts, and, eventually, the Continental ContiSportContacts.
The main mission of the CLS55 AMG seems to be to achieve a feeling of "very quick and yet totally unhurried." This car is a sleeper-until you nail the throttle, summon the grunt, and zoom yourself toward the horizon. At 5:00 on a Sunday morning or for a couple of laps on your favorite circuit, the M6 is faster, more rewarding, and more fun to drive. But at just about any time and in any other driving environment-day-to-day, for instance-the Mercedes-Benz is a more relaxing choice.
It also is a more cossetting car, although the ergonomics, the materials, and the perceived quality are disappointing. The matte wood looks as if came out of a tube, the white instrument faces are about as up-to-date as a midi skirt, and the Comand system is complex and confusing.
Unfortunately, with the exception of two beautiful round dials, the cockpit of the BMW is even less engaging. There are slabs of gratuitous carbon fiber, an impossibly wide transmission tunnel, an offset and thus more inconvenient iteration of the infamous iDrive controller, and rear visibility on par with a World War I submarine. Don't try the rear seats at all, by the way-unless you are under sixteen years old or really desperate for a lift.
Before we set off for our trans-alpine tri-country drive, this looked like a no-brainer: on paper, the BMW was the winner. But at the end of day three, it transpired to be a much closer match than expected. Without any doubt, the M6 is the sportier sport coupe. On sheer ability, the Bavarian two-plus-two is occasionally in a class of its own. In terms of charm and charisma, however, the AMG car has the edge.
Which one to choose? Great cars though they are, it would be best to wait for the BMW M5 with a manual transmission. At about $85,000, it should be priced about the same as a base CLS55 AMG and thousands less than the M6. Not only does it feature no-frills shifting, it also offers plenty of room for passengers and luggage and has enough stealth to fool uninformed law enforcement officers. It promises to be the smartest buy by a long shot, available at a BMW dealer near you in late 2006.