If I'm anything, I'm realistic. Spending a week driving two of the biggest vehicles on the road reminded me that some cars sell themselves. What I mean by that is that SUVs such as the 2015 Chevrolet Suburban and 2015 GMC Yukon XL will sell regardless of what people like me say about them. Customers want these capable 3-ton giants to haul around a few kids and associated gear for reasons beyond my comprehension. So let me save you some time. Are these better than the previous generation of GM SUVs? Yes. Without question, the interiors are a huge step up, they look more intimidating, and they get slightly better gas mileage. There you have it -- stop reading and go buy one.

Our test Chevy Suburban was a 4WD LTZ model powered by a 5.3-liter, 355-horsepower OHV V-8. It cranks out 383 lb-ft of torque at a relatively high 4100 RPM -- I say relatively high because that torque peak is only 1700 RPM short of redline. The big V-8 rumbled from 0-60 mph in 7.3 seconds and through the quarter mile in 15.7 seconds at 88.6 mph. For comparison, a Mercedes-Benz GL350 Bluetec gets to 60 mph 0.2 second slower and runs a 15.7-second quarter mile at 85.5 mph. The difference is that the GL is powered by 3.0-liter turbo diesel with 240 horsepower and 455 lb-ft of torque. Now you're probably saying, wow, comparing a Chevy Suburban to a Mercedes doesn't seem appropriate. But at $65,695, this Suburban's base price is $2390 more than the GL's. A Dodge Durango Citadel with a 5.7-liter Hemi V-8 and AWD is only 45 grand. As optioned, this particular Suburban would set you back $71,385. Yeah, let that sink in for a minute.

So how does it handle? After finishing the figure eight, our testing guru Kim Reynolds remarked, "I can't believe how good this is at the limit, after how disappointing it is on the street." Needless to say, he hadn't been impressed with the Suburban's behavior driving it home the previous evening. Kim was able to turn a 28.4-second lap with an 0.62 g average. The GL350 does the same lap in 28.7 seconds with a 0.54 g average. The Mercedes' downfall is its inability to disable an overbearing stability control system, which thankfully GM has decided isn't necessary on the Suburban. On the road the big Chevrolet feels absolutely trucklike. Its size is always at the forefront, with every one of those 5952 pounds reminding you the laws of physics aren't on your side. On the figure eight it turns in reasonably well. While the brakes aren't necessarily confidence-inspiring on the road, they will haul the Suburban down from 60 mph to 0 in 126 feet; the GL does it just 4 feet shorter.

If the $71,000 Chevy Suburban seems too plebian for you, how about its GMC sibling, the Yukon Denali XL? With a base price of $69,375 and an as-tested price of $77,965, you must really need that extra cargo space compared to something like the GL450, which currently sits at a base of $65,475. The Expedition King Ranch EL 4WD, which starts at $60,050, is the more natural competitor to both GMs, but we haven't touched one in more than 6 years, so the test data isn't exactly relevant.

The 2015 Yukon Denali is powered by a 6.2-liter, 420-horsepower V-8 that twists out 460 lb-ft of torque. While that is significantly more torque than in the Suburban, the delivery feels the same on the road, with several downshifts of the six-speed auto needed for passing. At the dragstrip, the extra power is noticeable, as the Denali turns in a 0-60 mph time of 6.2 seconds. That's a pretty impressive time for a vehicle weighing 6033 pounds, and it's backed up by a quarter-mile time of 14.7 seconds at 94.4 mph. If you're wondering about the less expensive 5876-pound Mercedes, it runs to 60 mph in 6.0 seconds and through the quarter in 14.5 seconds at 96.6 mph. The GL's twin-turbo V-8 is only producing 362 hp and 406 lb-ft of torque, but it makes it over a much larger area of the RPM range.

The Yukon Denali was also equipped with the magnetorheological suspension we have loved so much on everything from Corvettes and Camaros to Cadillacs. On the road, the ride quality isn't any better than in the Suburban. We attribute that to the optional bling-tastic 22-inch wheels instead of the standard 20s. Sure, the ride quality might be worse with the giant wheels, but can you put a price on rollin' hard in the most ballin' whip dropping off cupcakes at the PTA bake sale? Around our figure eight, the Denali put in a 28.4-second lap with a 0.64 average g. The GL450 ran a 28.5 at 0.56 average g. Again, Reynolds liked how the Denali felt on the figure eight. Several staffers -- myself included -- noted the very trucklike ride of the Yukon in most situations.

If there were a payoff for the more utilitarian nature of the body-on-frame Yukon, it might be easier to accept. The low front air dam, which was scraped on driveways throughout the week and restricts ground clearance to less than that of the front of several family sedans we had around, ruins any attempt at calling this an off-road vehicle. If it were available with ride-height-adjustable air suspension, like that available on the GL and several others competitors, it would go a long way. You can bring up the towing argument, and with a maximum tow rating of this Denali at 7900 pounds, that is a full 400 pounds -- roughly 5 percent -- more than either GL mentioned. The Suburban is rated at 8000 pounds. Again, the big and maybe only advantage of the big GM SUVs appears to be the cargo space behind the third-row seat.

We were able to put both of the SUVs through Motor Trend's Real MPG Testing loop. Like GM's latest 1500 trucks, both V-8s use cylinder deactivation to try and eek out a little more economy. It seems to have worked, especially in the case of the Chevy Suburban. While the Chevy carries an EPA rating of 15/22 for city/highway mpg, our testing returned 15.2/22.3 mpg. The larger displacement Denali didn't fare quite as well trying to reach its EPA rating of 14/20 city/highway mpg, returning Real MPG test number of 12.4/19.2 city/highway. For the previous models, the Chevy was rated at 15/21 and the GMC at 13/18 city/highway mpg. If you are wondering about EPA numbers on the Mercedes GL450, it's rated at 14/19 mpg. If you haven't considered a diesel SUV such as the GL350, ratings of 19/26 should pique your interest.

It might sound like we are a little bit down on the giant GM twins, and honestly, we are. We know it is considerably cheaper for GM to build these with shared truck parts, but when they don't have the associated advantages, what value is that to the consumer? The prices have increased to a point where they are competing with the luxury SUVs of the world, and yet they don't have the refinement or features. Do we think anyone will cross-shop a Suburban or Yukon with a Mercedes, BMW, or Range Rover? Probably not. Ford is really the only manufacturer that challenges GM in terms of size, and Ford wins in towing capacity. If your argument is that you don't intend to tow or go off-road -- it's estimated conservatively that 85 percent of SUV owners don't -- then you might be better off looking a different type of vehicle entirely.