2006 Cadillac STS-v vs. 2006 Mercedes CLS55 AMG Interior & Exterior Comparison & Review

Things change when reengaging traction and stability controls and taking to public roads. Cadillac's StabiliTrak will fishtail the STS-v out of power-on turns, while the Benz's electronic stability program gets jiggy on the throttle and ABS, holding momentum on a tighter leash. Once grip reestablishes itself, the CLS55 becomes a runaway freight train, able to thrust itself past mere mortal V-8s as if they were stuck in neutral.

Cadillac's powerhouse is nearly as impressive, but the torque deficit is obvious through the seat of your pants. After hitting 105.7 mph in the quarter mile, the Caddy struggles to reach 140 mph on our track, while the Merc does 114.5 mph and continues on to 140 as if it's a day in the park. You won't legally, sanely drive that fast, but Cadillac will sell the STS-v in Europe in minute numbers (North American volume will be about 2000 per year) as an image builder. On the real autobahn, quick spurts to 250 kph (about 140 mph) aren't uncommon, so this matters. Braking and lateral grip figures reveal the cars to be equally matched.

Both have fine, stitched-leather instrument panels. GMPD contracted Drexel Meyer, which also does Maybach's leather, to handle the leather and suede hides on the STS-v's dash, seats, and door panels. And it has heated rear seats, while the Benz has them only up front. But the Cadillac driver seat isn't as comfortable for long hauls, especially compared with the Mercedes's well-bolstered perforated leather and suede front seats. The v treatment is added to an STS interior, but falls short of its luxury intentions. This (admittedly good) patch job can't match an interior designed richly from the carpeting up, especially now that Mercedes is rebounding on interior quality.

Among the CLS55's many interior tricks is its dynamic driver's seat, in which the bolsters hold you in turns at the press of a button. Turn left, and the right bolster pumps up, and vice versa. It seems overwrought when gently changing lanes, but it's good on tight turns.

Standard nav systems, monthly-fee satellite radio, and cruise control help eat up a 785-mile round-trip. Neither navigation system is easy to use, sometimes providing incorrect information (note to Cadillac: Milwaukee has more than four hotels). And Cadillac's GM cruise control doesn't have a cancel switch. Mercedes's nav system (which doesn't have a "lawyer" screen you must acknowledge before using it) is better, but only by virtue of not being as confusing or confused as the Cadillac's. Mercedes's Sirius sat radio and Cadillac's XM have good selections of clear, digital sound.