The SL-Class’ front seatbelts will tighten automatically in the event the vehicle detects an impending crash, improving protection against injury significantly. The DB9 doesn’t offer pre-crash pretensioners.
The SL-Class has standard tall side airbags which act as a forgiving barrier between the driver and outboard passenger's upper bodies and the window and pillars. Combined with high-strength steel door beams and lower side airbags this system increases head protection in broadside collisions. The DB9 doesn't offer side airbag protection for the head.
The SL-Class has standard NECK-PRO Head Restraints, which use a specially designed headrest to protect the driver and front passenger from whiplash. During a rear-end collision, the NECK-PRO Head Restraints system moves the headrests forward to prevent neck and spine injuries. The DB9 doesn’t offer a whiplash protection system.
The SL-Class offers an optional PRE-SAFE Brake, which uses forward mounted sensors to warn the driver of a possible collision ahead. If the driver doesn’t react and the system determines a collision is imminent, it automatically applies the brakes at full-force in order to reduce the force of the crash or avoid it altogether. The DB9 doesn't offer crash mitigation brakes.
The Mercedes SL-Class has Daytime Running Lights to help keep it more visible under all conditions. Canadian government studies show that driving with lights during the day reduces accidents by 11% by making vehicles more conspicuous. The DB9 doesn’t offer Daytime Running Lights.
The SL-Class’ optional lane departure warning system alerts a temporarily inattentive driver when the vehicle begins to leave its lane and gently nudges the vehicle back towards its lane. The DB9 doesn’t offer a lane departure warning system.
The SL-Class’ optional blind spot warning system uses digital cameras monitored by computer to alert the driver to moving objects in the vehicle’s blind spots where the side view mirrors don’t reveal them and moves the vehicle back into its lane. The DB9 doesn’t offer a system to reveal objects in the driver’s blind spots.
The SL-Class’ driver alert monitor detects an inattentive driver then sounds a warning and suggests a break. According to the NHTSA, drivers who fall asleep cause about 100,000 crashes and 1500 deaths a year. The DB9 doesn’t offer a driver alert monitor.
The SL-Class has standard mbrace, which uses a global positioning satellite (GPS) receiver and a cellular system to remotely unlock your doors if you lock your keys in, help track down your vehicle if it’s stolen or send emergency personnel to the scene if any airbags deploy. The DB9 doesn’t offer a GPS response system, only a navigation computer with no live response for emergencies, so if you’re involved in an accident and you’re incapacitated help may not come as quickly.
Both the SL-Class and the DB9 have standard driver and passenger frontal airbags, front side-impact airbags, front seatbelt pretensioners, four-wheel antilock brakes, traction control and electronic stability systems to prevent skidding.
The SL-Class comes with a full 4 year/50,000 mile basic warranty, which covers the entire car. The DB9’s 3 year basic warranty expires 1 year sooner.
There are almost 26 times as many Mercedes dealers as there are Aston Martin dealers, which makes it much easier should you ever need service under the SL-Class’ warranty.
The SL550’s standard 4.7 turbo V8 produces 59 lbs.-ft. more torque (516 vs. 457) than the DB9’s 5.9 DOHC V12. The SL63 AMG’s standard 5.5 turbo V8 produces 20 more horsepower (530 vs. 510) and 133 lbs.-ft. more torque (590 vs. 457) than the DB9’s 5.9 DOHC V12. The SL63 AMG’s optional 5.5 turbo V8 produces 47 more horsepower (557 vs. 510) and 207 lbs.-ft. more torque (664 vs. 457) than the DB9’s 5.9 DOHC V12. The SL65 AMG’s standard 6.0 turbo V12 produces 111 more horsepower (621 vs. 510) and 281 lbs.-ft. more torque (738 vs. 457) than the DB9’s 5.9 DOHC V12.
On the EPA test cycle the SL550 gets better fuel mileage than the DB9 (16 city/24 hwy vs. 13 city/20 hwy). The SL63 gets better fuel mileage than the DB9 (16 city/25 hwy vs. 13 city/20 hwy).
In heavy traffic or at stoplights the SL-Class’ engine automatically turns off when the vehicle is stopped, saving fuel and reducing pollution. The engine is automatically restarted when the driver gets ready to move again. (Start/Stop isn’t accounted in present EPA fuel mileage tests.) The DB9 doesn’t offer an automatic engine start/stop system.
For better traction, the SL-Class has larger front tires than the DB9 (255/40R18 vs. 245/35R20).
Changing a flat tire near traffic can be dangerous and inconvenient. The run-flat tires available on the SL-Class can be driven up to 50 miles without any air pressure, allowing you to drive to a service station for a repair. The DB9 doesn’t offer run-flat tires.
The SL-Class offers an available adjustable active suspension system, which counteracts cornering forces actively, limiting body roll and improving handling and stability. Aston Martin doesn’t offer an active suspension on the DB9.
The SL-Class offers an optional automatic front and rear load leveling suspension to keep ride height level with a heavy load or when towing. The DB9 doesn’t offer a load leveling suspension.
For better handling and stability, the track (width between the wheels) on the SL-Class is .9 inches wider in the front and 1.5 inches wider in the rear than on the DB9.
For better maneuverability, the SL550’s turning circle is 1.5 feet tighter than the DB9’s (36.2 feet vs. 37.7 feet). The SL63/SL65’s turning circle is 1.4 feet tighter than the DB9’s (36.3 feet vs. 37.7 feet).
The SL-Class is 4.2 inches shorter than the DB9, making the SL-Class easier to handle, maneuver and park in tight spaces.
The design of the Mercedes SL-Class amounts to more than styling. The SL-Class has an aerodynamic coefficient of drag of .29 Cd. That is significantly lower than the DB9 (.35) and many sports cars. A more efficient exterior helps keep the interior quieter and helps the SL-Class get better fuel mileage.
The SL-Class’ standard power retractable hardtop allows a seamless transition from an open car, to a completely sealed coupe. The DB9 doesn’t offer a retractable hardtop.
The SL-Class has 2.4 inches more front headroom and .1 inches more front legroom than the DB9.