For decades now, Mercedes-Benz flagship sedans and coupes have been benchmarks for the rest of the automotive industry, representing engineering excellence, opulent luxury and state-of-the-art features that often not only trickle down to cheaper Mercedes models, but to other brands as well. That certainly applies to the 2015 Mercedes-Benz S-Class, a car that feels every bit as special and potentially groundbreaking as its illustrious predecessors.

After the current, all-new generation debuted last year, 2015 sees some previous family members return. The V12-powered S600 and S 65 AMG models rejoin the S-Class lineup after a year off, with the former boasting a bigger and more powerful engine than the previous generation's version. Most notably, though, the S-Class coupe name makes its return after nearly two decades. Like the CL-Class it replaces, though, the new S-Class coupe provides the same opulent interior quality and driving experience as the S-Class sedan, but with sleeker, two-door styling highlighted by a lack of a central B-pillar. As a result, there's really nothing like windows-down motoring in a big Benz coupe.

These new additions only bolster the S-Class' status as one of the finest cars on the road. Indeed, the latest-generation sedan feels like a step above traditional, admittedly cheaper competitors like the Audi A8 and BMW 7 Series in its design, quality, technology and overall luxury ambience. Instead, it seems far closer to an upper-echelon brand like Bentley -- especially the coupe, which stands as the only real apples-to-apples competitor for the Bentley Continental GT. No matter what you compare them to, however, the 2015 S-Class sedan and coupe definitely can be considered benchmarks.

The 2015 Mercedes-Benz S-Class is a full-size sedan and coupe available in a number of variants, which correspond to engine. Both body styles are available as an S550, S 63 AMG and S 65 AMG, while the sedan adds an additional S600 and S550 Plug-In Hybrid.

Standard equipment on the S550 models includes an adjustable air suspension, all-LED lighting (including adaptive headlights), automatic wipers (with advanced washers and heated blades), cruise control, dual-zone automatic climate control (with air purification and cabin fragrance systems), 12-way power front seats (with heating and memory settings), leather upholstery, a power tilt-and-telescoping steering wheel, MB-Tex synthetic leather interior trim, auto-dimming mirrors, soft-close doors, a power trunk lid and a power rear sunshade. A panoramic sunroof is standard on both body styles, but the coupe's features Magic Sky Control, which applies varying degrees of tint at the push of a button.

Standard electronics features include the COMAND interface (with two 12.3-inch display screens and a touchpad/rotary knob controller), a rearview camera, Bluetooth phone and audio connectivity, a navigation system, real-time traffic and weather, voice controls, an in-car WiFi hotspot, Mercedes mbrace telematics and a 13-speaker Burmester surround-sound audio system with a six-CD changer, two USB audio inputs, an iPod interface, HD and satellite radios, TuneIn Internet radio and 10GB of digital music storage. The sedan has 18-inch wheels. The coupe has 19-inch wheels, front and rear parking sensors, an automatic parallel parking system, keyless ignition and entry and upgraded leather upholstery. All are available on the sedan.

The sedan's Premium 1 package adds the front and rear parking sensors, automatic parallel parking system and keyless ignition and entry. It also includes a hands-free trunk opening, power rear side window shades and heated and ventilated active multicontour front seats (with additional adjustments, six massage programs and rapid-heating functionality).

The coupe's Premium 1 package adds the active multicontour front seats, a head-up display and a surround-view parking camera system.

The S 63 AMG includes all of the above, but gets a different engine and transmission, 20-inch wheels, sport-tuned suspension components, more aggressively bolstered seats and styling differences.

The following are options on the S550 and the S 63 sedans. The Driver Assistance package adds adaptive cruise control (with steering assistance and automated braking and accelerating) and a variety of electronic safety aids detailed in the Safety section below. The Rear Seat package adds four-zone automatic climate control, rear seatbelt airbags, upgraded headrests and power-adjustable rear seats (available separately). The Warmth & Comfort package also provides the power-adjustable rear seats, but adds heating and ventilation, front and rear heated armrests and a heated steering wheel. The Executive Rear Seat package adds "multicontour" rear seat adjustments and a passenger-side rear seat that features extra reclining and an extending footrest.

The S550 and S 63 coupes also can be had with the Driver Assistance package and their own Warmth & Comfort package, which has heated rear seats and a heated wood and leather steering wheel.

Stand-alone options on the S550 and S 63 sedans and coupes include a night vision system, upgraded leather upholstery, a 24-speaker Burmester 3-D surround-sound audio system and a heated steering wheel. Magic Body Control suspension, the surround-view camera and heated rear seats can be added separately to the sedan models.

All of the above options are standard on the S600 and S 65 AMG. The latter also gets the S 63's AMG-specific performance items.

Stand-alone options on all S-Class sedan models include a head-up display, a refrigerated rear center console, a heated windshield and a split-view front center display screen (also available on the coupe: driver and passenger can see different things). A fixed center console with heated and cooled cupholders and two airplane-style fold-out tables can be added to the Executive Rear Seat Plus package. There are also a variety of special "designo" paint, leather colors and trim types available.

Carbon-ceramic brakes can be added to the AMG models.

The 2015 Mercedes-Benz S550 is powered by a turbocharged 4.7-liter V8 engine good for 449 horsepower and 516 pound-feet of torque. A seven-speed automatic transmission and rear-wheel drive are standard on the sedan. 4Matic all-wheel drive is optional on the sedan and standard on the S550 coupe. At the Edmunds test track, a rear-wheel-drive S550 sedan went from zero to 60 mph in 4.9 seconds, which is quick but ultimately on par with similarly powered flagship luxury sedans. A S550 coupe 4Matic in our testing reached 60 mph in 4.7 seconds. EPA-estimated fuel economy for the S-Class varies by engine, and is 20 mpg combined (17 city/26 highway) for the S550 sedan. Opting for 4Matic all-wheel drive lowers those figures to 19 mpg combined (16/26). The coupe is rated at 19 mpg combined (16 city/24 highway).

The S600 has a turbocharged 6.0-liter V12 good for 523 hp and 612 lb-ft of torque. The seven-speed automatic and rear-wheel drive are standard, and 4Matic is unavailable. Mercedes estimates it will reach 60 mph in 4.5 seconds. EPA-estimated fuel economy is 15 mpg combined (13 city/21 highway).

The S 63 gets a turbocharged 5.5-liter V8 that produces 577 hp and 664 lb-ft of torque. A more performance-oriented version of 4Matic and a different, specialized seven-speed automatic transmission are standard. In Edmunds testing, the S 63 sedan hit 60 mph in 4.6 seconds. Mercedes estimates the S 63 coupe will get there in 3.9. Fuel economy estimates for the sedan and coupe stand at 18 mpg combined (15 city/23 highway). The sedan achieved 16.5 mpg on the Edmunds mixed-driving evaluation route.

The S 65 gets a different turbocharged 6.0-liter V12 good for 621 hp and 738 lb-ft of torque. It gets the same performance-oriented transmission as the S 63, but rear-wheel drive is standard on both the sedan and coupe. Mercedes estimates they will both reach 60 in about 4 seconds -- a number that doesn't really speak to their prodigious power. Fuel economy estimates are 15 mpg combined (13/20) for the sedan and 16 mpg combined (13/21) for the coupe.

Finally, the S550 Plug-In Hybrid features a turbocharged 3.0-liter V6 engine and an electric motor integrated within the seven-speed automatic transmission. Together, they generate a total of 436 hp. A lithium-ion battery resides under the trunk floor and should be recharged in less than three hours. This S-Class Plug-In Hybrid can drive using only electric power, unlike the previous-generation's mild-hybrid S400. Expect an electric-only range of about 20 miles and a 0-60 time of about 5 seconds. No EPA fuel economy estimates were announced at the time of this writing.

Every 2015 Mercedes-Benz S-Class comes standard with traction and stability control (with crosswind mitigation), antilock brakes, front and rear side airbags, full-length side curtain airbags and a driver knee airbag. Standard electronic safety features include a rearview camera, a driver inattention warning system and a collision prevention system that will warn the driver of a potential collision and fully apply the brakes if necessary.

The Driver Assistance package (standard on the S600 and S 65) includes an active blind-spot warning system (will steer you back to your lane if you fail to heed its warning), an active lane-departure warning system (ditto), pedestrian recognition for the collision prevention system, a rear-impact detection and preparedness system and an advanced adaptive cruise control system that not only matches the speed of the car in front of you, but will also apply the brakes and accelerator in stop-and-go traffic and keep you in your lane. Effectively, it drives for you on a gridlocked freeway.

Other options include a night vision system (detects pedestrians and animals through infrared sensors and displays them in the instrument panel) and a surround-view parking camera system. Mercedes' mbrace emergency telematics includes automatic collision notification, stolen-vehicle location assistance, alarm notification, an SOS emergency services button, geo-fencing for valets and teenage drivers and remote vehicle controls (via mobile app or computer) that can unlock or lock the car, for instance.

In Edmunds brake testing, an S550 sedan with all-season tires came to a stop from 60 mph in a short 115 feet. The S550 coupe with summer tires stopped 2 feet shorter. An S 63 AMG sedan stopped in 108 feet, which is typical for a performance car on summer tires.

Effortless. That's how the 2015 Mercedes-Benz S-Class feels when you're behind the wheel. The steering is fairly light, and when equipped with lane-keeping assist and/or Distronic Plus cruise control, it will even subtly steer the car for you. Still, you'll be surprised at how adeptly this very large sedan and coupe will hunker down and go around a corner. So well-rounded is the S-Class Sedan that it earned an Edmunds "A" rating for both the S550 and S 63 AMG. It should come as no surprise then, that the S550 Coupe also earned our top "A" rating as well.

You may think you've enjoyed a comfortable ride before, but it most likely pales in comparison to the adjustable air suspension fitted as standard to the S-Class. Not only does it iron out bumps, it does so without a hint of floatiness. Plus, the ride gets even better with the sedan's optional Magic Body Control. Utilizing a windshield-mounted camera, the car detects bumps and other imperfections in the road ahead and automatically adjusts the air suspension to compensate. We're not exaggerating when we say that large speed humps can feel more like pebbles.

The way the regular S550 gets up to speed is also, well, effortless. Acceleration from the turbo V8 is ferocious, yet its noises are reduced to a whisper inside the cocoon-like cabin. You're more likely to hear the AMG models, but they're not as vociferous as other AMG models. You're also more likely to get into trouble with Johnny Law since they get up to speed quicker than many sports cars.

The cabins of most flagship luxury cars feel like bigger, fancier versions of "lesser" models, sharing a general design aesthetic and many control components. Not so the 2015 Mercedes-Benz S-Class. Even within the company, there is a clear differentiation between it and other Mercedes models, indicating that this is a special car that exists above the rest. Even things like the seat control buttons are bespoke to the S-Class. More important, however, there is an elegance and sense of opulence here that make it feel more like a competitor for a Bentley than a BMW.

Beyond aesthetics, few cars can approach the new S-Class' comfort and infotainment features. The standard seats are lovely, but you'd be nuts not to select the Premium 1 package's multicontour seats with their additional adjustments, ventilation and six massage settings. That's right, six. One even simulates a hot stone massage by utilizing the seat's heating elements. And just in case your rear passengers are the jealous sort, the same opulent front seat features (including adjustments) are available in the sedan's enormous backseat. Plus, you can add an entertainment system, airplane-style pop-out tables and even a fridge. Those aren't available on the coupe, but even its backseat is pretty generously sized for a two-door car.

All of its many infotainment functions are controlled by the latest iteration of Mercedes' COMAND system, which remains one of the most user-friendly around (even if its immense number of functions renders it a tad overwhelming at first). Compared with the setup in other Mercedes-Benz models, the S-Class' upgraded COMAND interface features a colossal central screen, unique graphics, a new-for-2015 touchpad controller and a different physical button layout (buttons for frequently used functions are grouped around the main control knob rather than on the dash). Immediately adjacent to the infotainment screen is the instrument panel, which itself is an equally large display screen complete with simulated digital gauges.

The trunk, as you might expect from a 17-foot-long sedan, is sufficiently large at 16.3 cubic feet. Note, however, that the available 24-speaker Burmester high-end sound system "significantly" reduces trunk space, according to Mercedes. The S550 Plug-in Hybrid also has a smaller trunk (12.2 cubic feet) because of its battery pack.