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.