Each of the four models comprising the Mercedes SL-Class has its own personality. The SL550 weighs less than its siblings and is nimble and tossable, though it's more of a touring car than a pure sports car. Its 5.5-liter V8 puts out 382 horsepower at 6000 rpm and 391 pound-feet of torque from 2800 to 4000 rpm. The V8 emits a barbaric growl that is uncharacteristic for a Mercedes. The engine provides willing power at all rev ranges, and motivates the SL550 from 0-60 mph in 5.3 seconds. The transmission is a seven-speed automatic with a manual shiftgate and available steering wheel shift paddles. It has Comfort, Manual and Sport settings. The Comfort setting shifts up quickly to save fuel, which means immediate power won't always be on tap. The Sport setting holds gears longer to keep power ready, and upshifts and downshifts can sometimes feel abrupt. The Manual mode gives the driver the option of picking the gears. Gears can also be selected manually in the other modes.

The SL600 is more refined than the SL550 but not as sporty. It has a lot more immediate grunt, but is much more subtle in announcing its presence. The SL600's V12 engine puts out 510 horsepower at 5000 rpm and 612 pound-feet of torque from 1900 to 3500 rpm (221 more than the SL550). It has a five-speed automatic transmission that shifts smoother than the SL550's seven-speed. The SL600 can accelerate from 0 to 60 mph in 4.4 seconds, a benefit of its torque. The heavier engine, however, makes it less nimble than the SL550, making the SL600 even more of a tourer versus the sporty nature of the SL550. It'll easily best the SL550 in a straight line, but will lose ground in the turns.

The new SL63 AMG offers the best combination of power and handling. It is a meaner version of the SL550 in terms of power and is even better when it comes to handling. It cranks out 518 horsepower at 6800 rpm and 465 pound-feet of torque at 5200 rpm. The SL63's 6.2-liter V8 barks like the biggest dog on the block at startup, under acceleration and during downshifts, and emits a constant background rumble while cruising. A freer revving engine, the 6.2 hits its redline at 7200 rpm, which is pretty high for a large V8. It comes with a new seven-speed automated manual transmission that Mercedes calls the Sportshift MCT 7. MCT stands for Multi Clutch Technology, and the multiple clutches allow this transmission to shift gears with no interruption in power delivery. The new AMG transmission has four driving modes, Comfort, Sport, Sport-Plus and Manual. Sport shifts 20 percent faster than Comfort, Sport Plus shifts 20 percent faster than Sport, and Manual shifts another 10 percent faster than Sport Plus, or 50 percent faster than Comfort. In Manual, shifts take only 100 milliseconds. The MCT also features multiple downshifts, from seventh to fourth or fifth to second, for example, with double-clutching, throttle blipping and perfect rev-matching in between; the Sport Plus program works like a skilled driver might to keep the engine in the power band for hard driving. It downshifts readily when you get off the gas, such as in a long sweeping turns, so maximum torque is on tap when you're ready for the power again. Mercedes quotes a 4.4-second 0-60 time for the SL63, and we believe it.

The SL65 AMG has a twin-turbocharged V12 that makes an astounding 604 horsepower from 4800-5100 rpm and a stump-pulling 738 pound-feet of torque from 2000-4000 rpm. Like the SL600, it is more subtle about its performance capabilities, issuing a subdued turbine-like hum. The SL65's 0-60 mph time is 4.2 seconds, and it feels even quicker. With just a 0.2-second difference in 0-60 times, you might think there wouldn't be much difference between the SL63 and the SL65. You'd be wrong. While the SL63 is a grunty, torquey beast, the SL65 delivers a rush of power that throws you back into your seat and feels like a jet taking off. It also has an unfortunate tendency to stand up and go, making the front end feel light and lessening the driver's sense of control. The feeling is similar to the clumsy feeling you get with torque steer in a front-drive car, only the SL is rear-drive. The SL65 is not the right choice if you're looking for pure sportiness, as the heavy engine makes it more nose heavy and less willing to cut through corners. However, for a pure rush of power and adrenaline, the SL65 is one of the fastest cars on the market today.

The price for all this power is poor fuel economy. Like the prices of these cars, if you have to ask, then you probably don't want to know, but we'll tell you anyway. The SL550 is EPA rated at 14 mpg city and 21 mpg highway, and the SL600 and SL65 burn premium gas at the rate of 11 mpg city and 18 mpg highway. The numbers weren't in for the SL63 at press time, but we're betting they won't be good.

Steering, handling and ride quality, on the other hand, are quite good. Every SL offers a pleasant ride that is surprising given how sporty these cars are. Even the AMG models, with their 19-inch wheels and stiffer suspension settings, are comfortable. Every SL also gets Mercedes' Active Body Control (ABC) suspension that has four-wheel level control, driver-selectable ride height settings, and automatic lowering at speed. ABC uses hydraulic, electronic and mechanical components to reduce body roll by a claimed 68 percent. Punch the button for ABC Sport mode and Mercedes says it reduces roll by 95 percent and tightens shock damping. In either mode, the SL exhibits little body roll. Raising the car will help you prevent it from scraping over curbs and when entering raised parking lots. The automatic lowering feature helps give the SL stability at speed.

The new Direct-Steer system works mechanically, providing variable assist based on steering wheel position. Direct Steer does in a purely mechanical way what BMW, Cadillac and others are trying to do with complex computers, algorithms, and pumps. The ratio is 15:1 in a straight line, such as on the highway. The ratio gets quicker as the wheel is turned, providing noticeably faster response when the steering wheel is turned 90 degrees and beyond. The yaw gain goes up quickly between 0 and 42 mph, then drops off markedly all the way to maximum velocity, so that the car remains stable at high speeds, but is quick to maneuver at parking speeds and in accident-avoidance maneuvers. In the real world that means smaller steering inputs are needed in tight turns, which makes the SL more stable and more nimble in the twisties. We drove several SL models with it and found it worthwhile, but it won't be available until later in the model year or for the 2010 models.

The brakes are adequate for everyday driving, but the SL550 and SL600 don't have the brakes to handle track time or long jaunts on mountain roads. We found the brakes began to smell after an hour or two on California's mountain switchbacks. Those who want a track worthy car will want an AMG model. The brakes on the SL 63 AMG are monstrous in size and thickness and we found them fantastic in terms of power, response, and freedom from overheating and fade. The car's substantial 4200-pound weight holds no problems for these brakes, no matter what the conditions.

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