When you consider how they came to be, the Range Rover and the GL-Class actually have a lot in common. In both cases, the parent company already had at least one potent off-roader (the Series III for Land Rover, and the G-Wagen for Mercedes) and wanted to expand the breadth of their brands by entering luxury territory. For the Land Rover, that decision came in 1970, when the Range Rover was introduced -- a vehicle fit for British royalty. With the Mercedes, this was far from the company's first foray into the premium category. It wasn't even its first carlike SUV -- the ML-Class has that honor. The GL-Class was more off-road capable than the ML, but not as purpose-built as the G. And over time, both became available as wonderfully over-the-top high-performance models.

What makes the GL-Class and the Range Rover especially appealing to us is that they offer luxury amenities as well as poise and confidence in the dirt. When we learned we'd have the chance to try out the high-performance versions of both, specifically the Range Rover Supercharged and the Mercedes-Benz GL63, we figured out where we would drive them, both on-road and off, and got ready for a week of fun.

But then there was a big hitch in our plans. While the Range Rover Supercharged comes equipped with a two-speed electronic transfer box with electronic center differential (Land Rover's words), and the GL is available with an Off-Road package (two-speed transfer case, skidplates, six-mode driving), that package isn't available on the AMG version of the GL. The AMG GL has all-wheel drive and a rather low airdam, so we wouldn't be going on trails. However, we still took them on the highway, through the city, on twisty roads, and in the dirt to see which high-performance version of these SUVs we preferred.

2nd Place: Mercedes-Benz GL63 AMG

While the lack of off-road equipment was a major strike against the GL63 in this comparison, there are a lot of positive things to say about the GL, and even more positive things to say about the AMG version.

The GL63 is powered by a 5.5-liter twin-turbo engine backed by a seven-speed automatic transmission. The engine puts out 550 hp and 560 lb-ft of torque; thanks to that, plus the sweet-sounding AMG-tuned exhaust, power flows freely throughout the rpm range. The exhaust made wonderful growling noises and terrific throttle blips when downshifting. It sounds like a sports car, something few three-row SUVs can boast. The transmission is smooth, with only the occasional harsh shift. Ride comfort was actually better here than in the non-AMGs we've tested. Despite the vehicle's size and weight (5787 pounds), the GL63 handled better than we expected, and better than a vehicle this size should. There wasn't a lot of body roll, and the GL felt stable.

However, in some ways this vehicle didn't differentiate itself enough from its non-AMG brethren. While the ride was nicer than in the 350/450/550s we've driven in the past, the difference in power with the 63 wasn't as dramatic as we expected. This Mercedes got to 60 mph from a stop in 4.7 seconds. That's only 0.4 second quicker than the GL550 we tested at Sport/Utility of the Year, and slower than the Range Rover Supercharged. Yes, the GL63 was faster than non-AMG GLs, but not in the head-snapping way you would expect in an AMG. One place the Mercedes did differentiate itself quite well was in braking: The GL550 we tested at Sport/Utility of the Year stopped from 60 mph in a short 116 feet, a very impressive distance. The GL63 stopped in only 104 feet. That's phenomenal.

The interior is very nice, as you would expect in a Mercedes-Benz. The Porcelain leather with black stitching and Piano Black accents throughout the interior, plus the Bang & Olufsen sound system, make the three-row cabin a warm, welcoming place to be. However, inside and out, there aren't a lot of cues that indicate you are driving an AMG vehicle. The leather isn't significantly better than in the rest of the GL line. The center stack has a lot in common with other Mercedes on the market, but it's a classy setup that looks better than the Range Rover's. The GL offers three-row seating, and the third row folds flat by pushing two rocker switches. That makes it easy to reconfigure the interior to prioritize carrying people over gear, and vice versa.

There are plenty of reasons the GL is Motor Trend's 2013 Sport/Utility of the Year, including versatility, comfort, capability, variety, and power. But when it comes to the AMG version of a vehicle, we expect notable differences between it and the rest of the Mercedes line. It felt more like a package added onto the GL than an AMG vehicle that was engineered from the ground up. As Motor Trend senior features editor Jonny Lieberman explains, "I'm just not exactly sure what makes this an AMG. The engine isn't holy Zeus powerful, especially in a truck this large. And while 560 lb-ft of torque is obviously more than anyone needs, AMGs aren't about needs. They're about complete lunacy. According to AMG, the GL63's big advantage over the GL550 is handling. Well, I'm just not feeling it. Put another way, if the GL63 does in fact offer superior handling to the lower-rung GL550, it's a moot point because the new Range Rover bests them both. Really, though, an AMG version needs to be on handling par with physics-defying mutants like the Porsche Cayenne Turbo and BMW X6M, but it just isn't. Since it isn't, the low prow of a front end just makes parking difficult and off-pavement excursions impossible for no good reason."

1st Place: Range Rover Supercharged

If the GL63 is a velvet hammer, the Range Rover is a quality precision tool. It feels light and nimble, is quick to respond to driver input, and while only 0.1 second faster to 60 than the GL63, felt much sprightlier off the line.

There is a big reason for this. The Range Rover has undergone significant changes for 2013. The new model is lighter by about 700 pounds than the outgoing model because of the liberal use of aluminum in the body. That means less mass for the 510-hp, supercharged 5.0-liter V-8 to push around (this Range Rover weighed 5542 pounds as tested), something that was instantly noticeable. The engine worked well with the eight-speed ZF transmission. The supercharged 5.0-liter doesn't sound as good as the AMG Mercedes, but the Range Rover is tremendous fun on twisty roads, much more so than the GL. The Rover was comfortable on the highway, too. While both vehicles have air suspension, the Range Rover's worked well to keep the ride comfortable on the highway and responsive on canyon roads, more so than the Mercedes'.

Its light weight and responsive air suspension make handling a pleasure. It is fast, too -- even though it just barely won an impromptu drag race with the GL, it felt a lot faster off the line. Braking was very good, but not quite as good as that of the Mercedes' -- the Rover took 14 more feet to come to a stop from 60.

The cabin is thoroughly modern and stylish, yet the company paid special attention to functionality. There are clever storage areas on the doors in which to stow small valuables where prying eyes wouldn't think to look. There's even a cooler in the center console. Materials quality is excellent, and the interior color combination is classy and elegant. However, the navigation screen is clunky to operate, and the system looks and feels like it's a generation older than the rest of the category. Overall, though, the cabin is comfortable and attractive.

With the new model also came a new version of Terrain Response. Terrain Response 2 is an update of the system that has arguably redefined the idea of off-roading (even Jeep is using something similar Alex Steele), making it as easy to go off-road as selecting the icon that matches the land you want to traverse. The new Terrain Response adds a new Auto setting, and the system is easier to use than before. When we drove the vehicles in Hungry Valley, the Range Rover was comfortable and highly capable on the trail. It used electronics and sensors to keep the Rover from losing traction. Its sport/utility capability also exceeds that of the GL on-road, where it has a higher towing capacity. In addition, during our evaluation, the Rover's fuel economy was better. The only thing it can't do is seat seven. (For that, you can get the LR4 or the 2014 Range Rover Sport.) Range Rover has made some excellent changes to the flagship vehicle for 2013, and it shows.

What's even more impressive is that the Range Rover Supercharged is less expensive than the AMG GL. And while it may seem silly to consider the idea of value when discussing vehicles that cost six figures, you do get more for the money with the Rangie. It outperformed the Mercedes at the track. It was more fun on twisting roads. It was better equipped to go off-road and can tow more. It'll take a future comparison to see if a GL with the On/Off-Road Package is better in the backcountry. But for now, if we had this much money to spend on a single vehicle, and wanted one that offered the best combination of performance, luxury, and capability, the Range Rover Supercharged would be our choice.