Comparo: Aston Martin V8 Vantage Roadster vs. Porsche 911 4S Cabriolet

Story and photos by John LeBlanc Let's assume 18th century math geek, Sir Isaac Newton, wasn't a "car guy." Yet his Third Law rather nicely sums up why Aston Martin's V8 Vantage exists: It's the "opposite reaction" to Porsche's forceful 911 Carrera. Until the two-seat V8 Vantage Coupe came along in 2005, Aston had only larger, and exponentially more expensive, 2+2 GT coupes selling in boutique numbers. That's why one of Ulrich Bez's first projects, when the former Porsche bigwig came over to the British brand in 2000, was to create a less expensive Aston to expand the brand's appeal and sales.

Now, instead of handing over $200,000 for a DB9 to gain entry to the exclusive Aston Martin club, a V8 Vantage Coupe gets you past the red velvet rope for the low-for-an-Aston-price of $131,500. But how does Aston's progeny compare against its inspiration from the driver's perspective? To find out, we lined up a $146,800 2008 V8 Vantage Roadster and a $134,370 2008 911 Carrera 4S Cabriolet.

SECOND PLACE: Aston Martin V8 Vantage Roadster It doesn't matter if the top is up or down: The Aston has a much cleaner look than the Porsche's contrived-looking humpback style. It's understandable if one is already smitten with the V8 Vantage Roadster's classic long hood and short rear deck looks. From inside the car, one sits low in the V8 Vantage's cockpit, gazing out over that long hood. There's little "base model" feel to be found here. Most of the leather-trimmed elements and controls are carried over from the bigger DB9. In general, the ergonomics are fairly conventional. The only negatives is the fussy chronograph-style driver's instrumentation that is sometimes hard to read at speed. Ah yes, driving fast: A situation that's easy to achieve with this car's powerful and rapturous eight-cylinder engine. Although Porschephiles will beg to differ, the V8 Vantage's eponymous 4.3-litre mill with 385 horsepower and 302 lb.-ft. of torque has one of the best soundtracks in the auto world. Velvety. Smooth. You pick. And the rest of the drivetrain measures up to the V8 Vantage's role as the Aston for drivers. The six-speed manual (a manumatic is a $4,000 option) has a clutch with proper feel. The gearbox has a nice, firm "right there" feel when you engage cogs, although it's not as mechanically accurate as the 911.

Sounds like a winner from the driver's seat, right? But to answer why the Aston ends up playing second to the Porsche's lead role, let's turn to our friend Sir Isaac's First Law about inertia. With an extra 290 kg over the Carrera 4S to carry around -- 1,710 in total -- the V8 Vantage Roadster's extra avoirdupois always makes itself be known. When pressing on, the baby Aston corners flat enough, and the suspension is well balanced with excellent turn-in characteristics. But there's always that residual heft to deal with. Imagine an evening of dancing after indulging at dinner. And in a straight line, the V8 Vantage is about half-a-second slower from 0-100 km/h than the Porsche at 5.0 flat. Finally, while buyers in this class could care less, the Aston sucks gas like an SUV, with an as-tested 18.5L/100 km; about 20 per cent more than the Porsche. BUY THIS CAR IF ... You've fallen in love with its V8 rumble and classic roadster good looks. You want to pretend you're James Bond's little sibling. You love the sound of its sonorous V8. DON'T BUY THIS CAR IF ... You want to take friends/family away with you on a weekend. You're often quoted as saying, "speed is such a relative thing." Your neighbour is the local Greenpeace warden.

Newton didn't have any laws pertaining to longevity. If he did, 2+2 Porsche's 911 -- in concept, a vehicle unaltered for more than 40 years -- would definitely qualify. And the 911's age old legend / persona / baggage are its greatest strengths -- and weaknesses. No doubt, there's a certain "been there, done that" with the 911's looks. But from the helm Porsche's steadfast commitment to developing the best sports car on the market pays off huge dividends. Except for a few flirtations with fours in the early years, one can always count on a flat six-cylinder engine hanging out behind the rear wheels in any of today's 911s. In this Carrera 4S model, all-wheel-drive and a larger and more powerful 3.8-litre six with 355 hp and 295 lb.-ft. are upgrades from the $105,800 rear-drive 325 hp base model. The Porsche's engine numbers may make it out to be the sand-in-the-face weakling to the Aston's muscle-bound beach boy image, but the 911 Carrera 4S's 1,420 kg curb weight bestows it with almost a 10 per cent better power-to-weight ratio. Equally rewarding for drivers, the more lithesome Porsche owns the Aston when it comes to steering, cornering and braking.

The 911's leanness also carries over to the cockpit. There's little new here for Porsche fans. The steering wheel promptly reacts to requests. And despite the front wheels delivering power, it still chirps back all the flaws of the road while the Aston smothers them in the name of comfort. Where the Vantage is all exaggerated motions, the Porsche is precise and mechanically accurate. The gearbox slides into gear with little effort, the clutch is liquid smooth, and the pedals are positioned for dancing. Get it right and the 911 reacts with confidence-inspiring obedience that the (relatively) sloppier V8 Vantage can only aspire to. Then there's the "4" in the 911's name. If Porsche's already done a fine job taming all three of Newton's laws of motion (despite the challenges of its rear-engine setup) then the all-wheel drive only adds to its competence when the roads get slippery. It also makes the 911 Carrera 4S a truly all-season roadster with a proper set of snow tires. BUY THIS CAR IF ... You like to drive with the top down to the ski hill. You are a slave to its surgical steering, stopping and cornering. You want to drive an icon. DON'T BUY THIS CAR IF ... You don't want to drive an icon. Your spouse thinks Porsche's are "so predictable."