(FORTUNE Magazine) – "If you're squeamish, sensible, or simply lack automotive lust, do not read on. In the name of journalism, I hit the road last week to test the mettle and metal of the new breed of high-performance German automobiles. My assignment was to single out the superlative vehicles based on aerodynamics, horsepower, adrenaline production, and overall gawk appeal. In selecting, I manhandled, skidded, screeched, drag-raced, redlined, and nearly rolled the top machines from BMW and Mercedes. It was not a pretty process. But from that elite lineup, two clear--and entirely different--leaders emerged.

I was selected for this mission because cars are my first passion: I have spent time on the racetrack in open-wheel competition and road-tested countless production vehicles, from Porsches and Lotuses to Vipers and pickups. I also stand behind the sweeping generalization that when it comes to car building, the Germans have everyone else whipped. There are nonbelievers, of course, who sneer at the sight of BMW's proud blue and white heraldry and Mercedes' haughty star. They prefer the unpredictable passions of Italian cars, the fair-weather fun of the British, the bulky oomph of the old Americans, the reverse snobbery of the Japanese. To me, none of those qualities is endurable in a mate, let alone in a machine to which you entrust your health and well-being. Give me physical prowess, scientifically consistent thrills, and understated elegance any day (and every day--I have never owned anything but German cars).

MERCEDES

I started--where else?--at the top, with Mercedes' SL600. As soon as I gripped the burled-walnut-and-leather steering wheel, I understood that this $120,100 convertible is the embodiment of decadence. There are enough elaborate systems, bells, and whistles to make driving the secondary activity. Don't get me wrong, the SL600 is a performance monster. But it is a domesticated beast (they don't even make a manual version) that moves the mountains for you so you don't have to lift a finger. In other words, Chanel would have been more appropriate than my red Nomex firesuit.

With a 48-valve, 12-cylinder engine producing 389 horsepower, the shiny black two-seater regally catapulted me through city traffic: an extremely classy dragster. I headed to the back roads around Bear Mountain Park, New York, to see how the Mercedes handled in curvier terrain. In the middle of a nice banked downhill turn, I was doing my usual--a tire-smoking sideways slide--when a giant can-opener noise erupted from behind me. It was the emergency roll bar popping up. This occurs when the car heels over to a 26-degree angle and one wheel leaves the ground. Oops. And just in case I needed even more help at that sticky moment, something called the Electronic Stability Program kicked in to 'maintain control by applying brake pressure to individual wheels.' I felt as if I were driving with a full staff of hired help, but, hey, thanks to all of them, I did manage an effortless 140 mph when I returned to the highway.

I awakened the roll bar several more times, but by then I had figured out some of the amusingly vague hieroglyphics on the interior controls, including the button that tucked the bar back in its cave. Other gadgets lured me in: seven Bose speakers to drown out the sumptuous motor, an integrated cellular phone, an electronic steering-wheel adjuster, a crowd-pleasing automatic roof act, and the most mysterious--heaters embedded deep down in the leather-swathed Recaro seats. No need went unmet, or perhaps I should say that every primal urge was lovingly refined and tidied up.

Because the SL600 is such a rare chariot (only 1,112 were made in 1995), I could almost forgive its intrusions on the driver. After all, its mission is to prove that with vast amounts of money come vast amounts of ease. Besides, I learned how to outsmart its autopilot tendencies and have some fun, including getting the SL600 to do zero to 60 in 5.9 seconds (remember that number for later). A final statistic: Each morning during testing (four in all), I received a proposal of marriage--from the Mercedes-smitten garage attendant.

BMW

Already married, I turned to BMW's impressive lineup. Given all the recent hype, I expected to be advising you to rush onto the waiting list for BMW's sexy new Z3 roadster. And I still might, if you're lonely or simply need attention: During my weekend with a lipstick-red model, a Porsche owner gave me the thumbs up; city kids yelled, 'Yo! It's the Bond car, man!'; and one poor cyclist hit a parked car mid-ogle. But the convertible's underwhelming four-cylinder engine left me flatfooted at more than one green light, and its soft suspension sent the car bouncing sideways on an uneven road. Without more power and tighter handling, this $28,750 car is destined to remain eye candy.

No, BMW's real racecar is the M3, which ironically lurks under the skin of a basic sedan (this, I figure, is how you hoodwink your mate into the purchase). In me, the car inspired reckless, I'll-regret-it-in-the-morning confidence. The sensation of pushing an M3 to its limits was similar to driving a motorcycle--lots of quick shifts and torque, lots of aggression and neck-snapping g-force. A trip to the store suddenly felt like outrunning the police to the border. Simple curves inspired visions of the corniche at Monaco. The damnedest thing was, the M3 backed me up through every grandiose stunt. Armed with a 240-horsepower in-line six-cylinder engine, taut suspension, hypersticky tires, and enormous disk brakes meatier than those on a Porsche 911 Carrera 4, the M3 is basically racetrack-ready. Did I mention the come-hither growl?

There's an elite skunkworks at BMW's Munich headquarters dedicated to developing these high-performance M cars. The group introduced its first M3 in 1987; by the end of that generation's production in 1991, it had become the most successful racer in touring-car history, winning 1,436 races and 50 worldwide championships. The new generation M3 outsold Porsche in the U.S. in 1995, a first.

I could load you up with even more numbers, ratios, and statistics, but the real point is that I, normally cool-headed in the driver's seat, fell hard for the M3.

On a more practical note: It's actually affordable at $38,960. Sure, there are V-8s and V-12s with greater raw power, but only a Formula Dodge racer has given me as strong a sense of oneness with the road. Besides, the M3 can do zero to 60 in 5.9 seconds--neck and neck with the Mercedes, but $81,140 less. Hell, for that price you can buy two more and share the sickness of competition with friends and loved ones.

My assignment complete, the gap between the German competitors was quite clear: BMW builds cars for drivers who want to be exposed to the rigors of performance, while Mercedes engineers its cars to buffer owners from those very same rigors. Depending on what you want, one will hold more appeal than the other.

Of course, there's a chance that with the introduction of the supercharged SLK two-seater later this year, Mercedes will wheel a more serious and affordable contender into the performance arena. (On the other hand, the company, oddly, is proud to explain that SLK is a German acronym that translates as 'sporty, light, and short'--hmmm.) And (my heart be still), BMW dangled a drool-provoking tidbit at this year's Geneva Auto Show: a Z3 with an M3-like performance package. Such a combination would turn what is now an alfresco joyride into unadulterated, blissful terror.

I'll be back."