NEW YORK (CNNMoney.com) - Does this sound like a strange idea to anyone else? A Jeep that goes zero-to-sixty in under five seconds. But you can't take it off road. Not even a little bit off road.

I admit, I'm a little baffled by the idea behind the Jeep Grand Cherokee SRT-8, a lowered-down Jeep with a 6.1-liter 420-horsepower V-8 engine. But it's an idea whose time must have arrived, given GM's recent release of the Chevrolet TrailBlazer SS, a similarly-sized SUV with a 6.0-liter 395-horsepower V-8 engine. That's the same engine used to power the Chevrolet Corvette sports car.

Chevrolet TrailBlazer SS (black) and Jeep Grand Cherokee SRT-8 (red).

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Given worries about gas prices, it may seem an awkward time to release vehicles like this. But these are niche vehicles, intended to sell to a few people who want to drive the fastest SUVs around but who can't afford a $90,000 Porsche Cayenne Turbo. There just aren't many people like that, though, so don't get too worked up about the impact on our nation's fuel consumption.

No question about it: The Jeep Grand Cherokee SRT-8 is a lot of fun. The performance and feel is similar to that available in other Chrysler Group SRT-8 products, such as the Chrysler 300 SRT-8, but there's something just so ridiculous about an SUV behaving this way that it makes it all seem even more entertaining.

Stomp hard on the gas and hold on tight as your stomach mashes itself against the back of your rib cage. Throw the SRT-8 into a turn and your shoulder digs into the seat's huge side bolsters.

It's easy to forget you're in an SUV as the truck's body stays nice and flat through turn after turn. The five-speed automatic transmission, left on its own, doesn't always downshift as quickly as it should, but you can select gears manually with side-to-side flicks of the gear selector, keeping the big engine revving near the top of its range through hilly, twisty roads.

Despite lacking off-road ability -- for one thing, the low-hanging front air dam would soon scoop up several pounds of small animals -- the Grand Cherokee does have full-time all-wheel-drive. But it's set up so that 90 percent of the power goes to the rear wheels until there's a real need for traction up front. It only lasts for a moment, but you can spin the rear wheels with ease.

There is a price to be paid for all this giddy fun, besides the aforementioned fuel costs. To get this kind of performance out of an SUV, the SRT-8 engineers had to make the suspension very stiff and the steering very sensitive. It feels more than fine on smoothly rolling rural roads, but the jarring ride in day-to-day driving will turn off a lot of SUV buyers who might otherwise be intrigued by the performance.

The Chevrolet TrailBlazer SS is a strong performer, as well, but it's not quite as much fun in hard-charging as the Grand Cherokee SRT-8. The steering feel is less direct and its four-speed transmission feels like it could use another gear. Also, the TrailBlazer SS's transmission isn't fully controllable, like the Jeep's is. You can move it into a lower gear range, of course -- that's what I did when tackling a steeply rolling mountain road -- but that's all. You can't quickly choose up- and down-shifts at will.

The seats also don't offer the kind of side-to-side support you get with the Jeep's deep-dish front seats.

According to manufacturer specs, the TrailBlazer SS is almost a full second slower zero-to-sixty than the Jeep. If no-one told you, though, you'd almost certainly never notice. Even in an SUV, that Corvette engine is powerful enough to pin you back in the seat.

While losing a little to the Jeep in all-out performance, the TrailBlazer takes a big lead in the "real world driving" category. Until you grind your shoe into the gas pedal, it actually feels more-or-less like a regular mid-sized SUV. In contrast to the Jeep, my passengers had no complaints in the TrailBlazer.

The interior door panels and dash were also looked and felt nicer than the unattractive hard plastics used in the Jeep.

Overall, if I had to pick between these two, I'd take the TrailBlazer in a second. Make that 5.7 seconds.

Photos and details:

Jeep Grand Cherokee SRT-8

Chevrolet TrailBlazer

(SS is an option package selectable under "pricing.")

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