As prevalent as it might be in these days of downsizing and budget cuts to dismiss full-size SUVs as relics of the past, they exist for very good reasons, most of which are clearly demonstrated by the 2011 Mercedes-Benz GL-Class. Despite the considerable price of ownership, the GL presents a perfectly logical argument for the existence of the seven-seat luxury vehicle, most particularly for large families who prefer to travel in style and a high level of safety through all types of weather.

Mercedes' three-row SUV is more egalitarian than any other model in the brand's lineup, sharing its wealth of space, comfort and safety features among all seven travelers. Every seat is a good fit, and even the two passengers relegated to the third row will have little reason to complain. Despite its plus-sized heft and girth, the GL is surprisingly light on its tires and carves through urban congestion like a wood nymph slipping quietly through the forest. And when the road starts to bend, the standard air suspension and all-wheel drive keep this Mercedes luxury liner on a smooth and even keel.

As a vehicle type, the GL is a crossover, which means it's built like a car and thus is better able to deliver superior road manners and interior packaging than truck-based SUVs. There are three GL models, two featuring V8 engines and one with a turbocharged clean-diesel V6. A diesel engine makes a lot of sense in a big and heavy SUV because of its muscular torque and superior fuel economy. In comparison, the GL diesel is just about as economical to operate as the Escalade Hybrid, which is slower, more cumbersome to drive and more expensive.

In fact, few other luxury SUV can deliver the same balance of driving refinement and interior space as the 2011 Mercedes GL-Class. The 2011 Lexus LX 570 has an edge when going off-road, but it's typically more expensive and not as roomy on the inside. Models like the 2011 Cadillac Escalade and 2011 Lincoln Navigator have the space but can't match the Mercedes' overall refinement. The new 2011 Infiniti QX56 and 2011 Land Rover LR4 are interesting comparisons as they provide similar space and power as the GL550 for considerably less money. But overall, we're pretty fond of the GL and find it a perfectly logical choice for those who need a full-size luxury SUV.

The 2011 Mercedes-Benz GL-Class is a full-size luxury crossover that seats seven people. It is available in GL350 Bluetec, GL450 and GL550 trim levels, which correspond to the engine choice. All GLs have standard all-wheel drive.

The GL350 Bluetec and GL450 are similarly equipped with an adaptive air suspension, a sunroof, automatic headlights, roof rails, automatic wipers, dual-zone automatic climate control, rear air-conditioning controls, heated eight-way power front seats, MB-Tex premium vinyl upholstery, burl walnut trim, third-row power split-folding seatbacks, the COMAND electronics interface, Bluetooth and an eight-speaker sound system with an in-dash six-CD changer and an auxiliary audio jack. The GL350 gets 20-inch wheels while the GL450 has 19s.

Selecting the Premium I package adds a power liftgate, power-folding mirrors, a rearview camera with integrated compass, upgraded front seats with memory functions, auto-dimming driver-side and interior mirrors, a hard-drive-based navigation system, voice controls, digital music storage, HD radio, an iPod interface and satellite radio. The Premium II package includes all the previous items plus keyless ignition/entry and a Harman Kardon surround-sound audio system.

The Full Leather Seating package adds leather upholstery, "comfort headrests" and ambient interior lighting. The Lighting package adds LED daytime running lights and adaptive bi-xenon headlights with washers. Parking sensors, running boards, ventilated and massaging front seats, and tri-zone climate control are also optional.

All of the above equipment comes standard on the GL550. To those items the 550 adds 21-inch wheels, performance tires and a more aggressive-looking front fascia. Stand-alone options available on all GL-Class models include a blind-spot warning system, a trailer hitch, roof crossbars, a wood-and-leather steering wheel, a heated steering wheel, a rear-seat entertainment system and heated rear seats.

The 2011 Mercedes-Benz GL350 Bluetec features a 3.0-liter diesel-powered turbocharged V6 with 50-state-legal clean diesel technology. This engine produces 210 horsepower and 400 pound-feet of torque. Like all GL-Class models, the V6 sends its power through a seven-speed automatic transmission and "4Matic" all-wheel drive. Though we haven't tested the latest GL diesel, we estimate it will accelerate from zero to 60 mph in 9 seconds. Fuel economy for the Bluetec is 17 mpg city/23 mpg highway and 19 mpg combined.

The Mercedes GL450's 4.7-liter gasoline-powered V8 is good for 335 hp and 339 lb-ft of torque. Tests show zero to 60 mph in a swift 6.7 seconds, and the estimated fuel economy is 13/17/14.

A jump up to the GL550 brings with it a 5.5-liter V8 delivering 382 hp and 391 lb-ft of torque. It accelerates from zero to 60 mph in 6.5 seconds, and the estimated fuel economy is 12/17/14. When properly equipped, each of the GL-Class models can tow up to 7,500 pounds.

Standard safety features on the 2011 Mercedes-Benz GL-Class include stability control, antilock brakes, a driver knee airbag, first- and second-row side airbags, full-length side curtain airbags and whiplash-reducing head restraints fitted to all seven seats. Hill start assist, hill descent control and the mbrace emergency system are also standard. A rearview camera, parking sensors and a blind-spot warning system are also standard or optional depending on the trim level. In Edmunds brake testing, we've measured an average stopping distance from 60 mph of about 124 feet -- excellent performance for a large luxury SUV.

There's no lack of power with either of the two V8s, and both are capable of smoking their competition. If getting off the line doesn't mean all that much to your driving pleasure, the GL350's V6 diesel is more economical but delivers plenty of low-speed punch around town and is so quiet only the badging gives it away. Quietness, in fact, is the GL's most endearing trait. The GL's handling is a bit soft for those who like to carve precise lines through the corners, but it's generally better than the handling from the truck-based behemoths. And though the 2011 Mercedes-Benz GL's steering might be a bit slow for sporty drivers, it's nicely weighted and provides excellent straight-line tracking.

The 2011 Mercedes-Benz GL's cabin is comfortable and luxuriously appointed. Fit and finish are superb, the seats are exceptionally supportive and headroom and legroom are ample in nearly every position. The COMAND electronics interface is finicky to use, employing awkward push-buttons on a center-stack-mounted circular control pad instead of the preferred console-mounted control wheel used in more recently introduced Mercedes-Benz models.

The GL is one of the most spacious luxury crossovers on the market, as its third row is big enough to seat two average-sized adults in comfort -- something the Audi Q7 can't claim. The second row could use a sliding adjustment, however, to allow for more legroom in both the second and third rows. The GL provides 83 cubic feet of maximum cargo volume, which falls below competing SUVs like the Infiniti QX56 and Land Rover LR4.