Jaguar XKR v Porsche 911 Carrera S Cabriolet v Aston Martin V8 Vantage Roadster

My credit card pops out of the machine. I pocket it, nose out of the toll lane and glance right just at the moment the other two cars emerge, like racehorses from their stalls. Perfect. I hit the throttle too.

All three cars have their roofs stowed, opening our ears to the full effect of their engines – the breathy whoosh of the Porsche’s flat-six, the crooning beat of the Jaguar’s supercharged V8 and, transcending them both, the hard, hammery note of the Aston Martin’s naturally aspirated V8. But the loudest car is getting gradually dropped as the ad hoc drag race develops. Our three-horse race becomes Porsche versus Jaguar as the French national speed limit comes up.

And relax.

I’m happy to chalk that one down to the Jag, which I happen to be driving. Roger Green in the Porsche might disagree, but over the next couple of days the Jaguar’s ability to get gone the moment the road is straight will impress us all. We’re hopeful that it will prove to be on the money when the road gets twisty, too.

There’s a new sense of purpose about the latest generation of Jaguars, particularly the ones powered by the all-new, 503bhp 5-litre supercharged V8, that gives you confidence that they can retain their traditional strengths while competing with ostensibly more sporting cars. In this instance that’s the 380bhp Porsche Carrera S Cabriolet and the 420bhp Aston Martin V8 Vantage Roadster.

We’ve driven both from the UK to the outskirts of Paris and collected the XKR from the wonderfully helpful people at Jaguar France. Back in Blighty it had taken seconds to decide which car photographer Stuart Collins and I were going to pack his gear and my bag into, the decision made when we popped open the Aston’s boot. The Porsche may be the smaller car but it’s more accommodating, offering boot space on a par with the Aston plus token rear seats (i.e. extra luggage space) like the much bigger Jaguar. You can either marvel at the Porsche’s packaging or wonder where all the space is squandered in the other two.

Refined this 911 is not, however. Not only is there a constant rustle of wind noise from the hood at a motorway pace but there’s also a low-pitched boom that makes conversation tricky. The Aston is better, attests our third tester, John Hayman, but it’s the Jaguar that proves the most refined, hood up or down. And we feel blessed that we are able to get the roofs down after driving through rain to get to Paris last night.

After stints in the 911 and Vantage, the XKR feels like it looks – huge. You drop down into the slim seats of the others but slide into the Jaguar’s chair, though with the push of a button you can tailor the upper body embrace, which helps. We’d prefer a knurled aluminium facia trim to polished wood, but let your eye wander the cabin and you’ll come to the conclusion that you’re in the best quality cockpit; moreover, the perfectly stitched leather of the seats and facia is standard where it’s a £2245 option on the Porsche. The Aston is far and away the most stylish of the three, though, and has beautifully tailored hide too. Shame about the cheap push- button switches and column stalks.

Because of its size the Jaguar feels the least intimate, and almost as soon as you’re rolling you’re aware that there’s a less direct connection between driver and car. Partly it’s the torque converter of the six-speed ZF auto, which fuzzes the throttle response at low speeds, partly the variable-assistance steering, which offers less resistance than expected as you twirl the wheel. The ride is pretty good, but having driven the XFR and read David Vivian’s report on the XKR coupe (evo 129), which is said to be just a few per cent different to the convertible, I was anticipating a little more directness.

The Porsche and Aston are much more closely matched. Right from the off the Carrera feels spot-on, its PASM adaptive damping (standard on the ‘S’) delivering a firm but supple ride, its nicely weighted steering clean, direct and full of feel, its brakes responsive from the top of the pedal but perfectly progressive too. Quality in the Porsche is more in the depth of feel than in the fixtures and fittings. We still wouldn’t go for the dual-clutch PDK transmission, though. It works well but we’ve never fancied an automatic 911 and those push-for-up, pull-for-down steering-wheel-mounted switches continue to annoy us.

A reminder of what you’re missing is provided by the V8 Vantage, which comes with a deliciously tactile, finely weighted and mechanically positive manual gearbox. The rear-mounted Graziano six-speeder is a beautiful thing, a fraction heftier in its action than the Porsche manual six-speeder but no chore, though the clutch action, improved over that of the early cars, retains a curiously numb biting point. The Aston’s steering is a bit beefier than the Porsche’s and this matches its general feel, while its ride for the most part is taut and absorbent but just occasionally caught out by sharp transverse ridges.

The sun may be a bit watery but it’s good enough for us, so all three hoods are stowed. Not for our trio the weight and packaging penalties of the now-popular folding hard-top. Instead they have fabric hoods with small glass rear screens that fold away under body-colour tonneaus. Well, mostly. The Aston’s stows under an attractive double-bubble cover, the Jag’s beneath a flush-fitting apron but the Porsche leaves a band of fabric on display. Probably saves a couple of kilos, and it all helps: even though the 911 is mostly steel while the British pair are aluminium, it’s by far the lightest. At 1510kg it’s 200kg lighter than the V8 Vantage, and almost 300kg lighter than the 1800kg XKR.

Being the biggest and roomiest, you expect the Jaguar will be the draughtiest on the autoroute. Not so. All three come with fine mesh guards that slot into place behind the seats and which very effectively eliminate the back-draught that can be so irksome and chilling. The XK is the best of all, just a carefully managed, gentle ruffling of your barnet at 80mph while you’re heated by the seats from beneath and bathed in warm air from the vents in front.

Our destination is the Normandy coast and once we’re off the autoroute and closing in on it, there are a few corners to get stuck into and roundabouts to be despatched. There’s no question that the XKR has got the newly developed active limited-slip diff. The new 5-litre V8 – purer sounding than the old engine with less supercharger whine – delivers an astonishing hit from low revs, yet the rear tyres have little difficulty laying this on the road. Drive is not something the rear-engined Porsche lacks either, and with its low weight and keen-edged 380bhp (that’s 5bhp more than the 996 GT3 of just four years ago!) it virtually matches the Jag yard for yard. In the dry the Aston finds strong drive too, though its 4.7-litre V8 doesn’t deliver the low-end punch of the other engines, only getting properly, irresistibly into its stride once the exhaust valve has opened and the tacho needle is swinging for 5000rpm.

And then we get a glimpse of the sea, all blue and spangly, and we slip effortlessly into loafing mode, happy to take in the view, listen to the gulls and anticipate the first whiff of ozone. Finding a beach you can drive down to on this bit of coastline is tricky, but we’ve done our homework on Google Earth and are soon wending our way to the surf.

If you want proof that the south coast of England was once connected to the northern coast of France, it’s here by the millions of tons – 100ft-high chalk cliffs, miles of them, that match those at Dover. ‘But how come the water’s blue on this side but brown on our side?’ asks Dover resident Hayman.

As Collins clicks away we get to muse on the aesthetics of our trio. Outgunned by the others it may be, but the Aston is no slouch and it’s undoubtedly the most handsome of the three, the chop seeming to have accentuated its squat, sleek shape. It certainly draws the most attention, though the fact that it’s an Aston, it’s painted neon blue and it sounds like an unsilenced race car above 4000rpm does help.

Porsche describes the colour of this Carrera S as ‘Macadamia’, which sounds like higher education in Scotland but is, apparently, a kind of nut. However you dress it up it’s metallic brown and it does the 911 few favours. Colour isn’t the only issue, though. The soft-top 911 suffers in two ways, the first being that it looks just like a £30K Boxster as it comes towards you, the second that it looks clumsy and fat-arsed as it goes by. The Jaguar hasn’t emerged from decapitation with its looks intact either; the XK looks quite bland without the rakish coupe roofline to tie it all together. But you can bet that all three were designed as convertibles from the outset, as parallel models to the coupes. They all weigh 50-90kg more than their hard-top equivalents and feel commendably solid, with minimal rear-view mirror shake.

Just up the coast from our beach we find a challenging stretch of road which, handily for us, is closed by road works at one end and so has little traffic on it. Snapper Collins sets up on one of its corners while we scoot backwards and forwards for the camera, Green in the XKR and me in the Carrera. Hayman is parked up the road in the Aston – it’s so loud that we elect to run it last just in case there are tucked-away households that might be upset by its penetrating bark.

It seems that Roger’s pants are on fire – as soon as we’re rolling, the rear of the Jag dips, there’s a hollow, insistent roar from its quartet of tailpipes and its chunky rump is gone. There are a couple of straights but, being quite narrow, this road is more suited to the 911 than the XK. There’s one particularly interesting and open corner sequence that helps define the dynamic character of each car. Going slightly downhill, it’s a clear-sighted, near-180-degree left that gradually opens out and goes up to a long, very- late-apex right.

I have to work the 911’s 3.8-litre flat-six really hard to stay with the XKR and it’s quite an experience, especially when Rog is downshifting into the tight corners and there’s a fantastic whip-crack of backfire. Any ground the Porsche loses on the straight is regained under braking and turn-in, but it’s the long turn that reveals most clearly what the Porsche has in hand.

You expect sensational rear grip and traction from a 911 but what you don’t appreciate initially is just how strong the front-end grip of the Carrera S is. With most of the car’s mass at the rear you’d think the lightly laden front would push into understeer, yet it doesn’t. I discover this when I turn PSM off to see if the rear will budge heading uphill. I turn in, power on, then give the throttle a big squeeze as I steer a bit harder for the late apex. It’s high-torque second-gear stuff yet the front tyres hold on tenaciously, as if there’s a Scalextric peg in the middle of the front axle picking up on an invisible slot. From entry to exit the Porsche can gain three car-lengths on the Jag, and when I swap seats with Rog, I can see why.

There just isn’t the bite on turn-in, the close body control and tenacity of grip. This is the most focused Jag for years yet straight after the Porsche you feel a little more remote from the action and less able to find the same degree of precision when you make inputs. Twisting the rotary gear selector from Drive to Sport helps sharpen up the shifts, but the Jag’s lighter steering feels a shade too sharp and the brakes are a little grabby too. To smooth things out you need to concentrate on making more sensitive inputs. The exception is the throttle, which you can simply stamp on, so amazing is the traction. It’s still brilliant if you switch off DSC entirely, though you have to be more aware of what you’re asking the rear tyres to do – catching slides is as much about prediction as reading what the car is telling you because the rear can step out quickly.

The Aston is more 911-like in its demeanour, with positive lines of communication through the steering and suspension. It’s pleasingly planted and precise, the chassis taking the unevenness out of the road as effectively as the others. The Vantage’s poise and directness are encouraging, and held supportively by the sculpted driver’s seat, you feel well placed to explore the car’s handling.

Its steering is very good, though not quite as fine as the 911’s, being a little heavier and less bright in its feel, while grip is good and traction solid. Ultimately it doesn’t demonstrate quite the unshakeable poise of the Porsche, its damping occasionally feeling a little soft at the end of a long, high-G curve, but it’s a satisfying car whose dynamics feel well matched to its performance. Shame it’s engine is so loud that everyone knows when you’re on it.

On more open, cross-country roads, the Jaguar can set a blistering pace, but the moment things get tighter and more interesting, it feels out of its comfort zone again. While the Aston and Porsche get stuck in, the Jaguar becomes less positive and less easy to place precisely, a trait most obvious under firm braking when the whole car seems to squirm slightly.

No question, the XKR is a great convertible, refined with the hood up or down, very well built and a great stress-free cruiser. It’s also astonishingly, effortlessly fast on open, flowing roads. In other words, a true Jaguar. However, it remains a GT rather than a sports car, feeling more like a successor to the fine Mercedes SL55 AMG than a direct rival for the Aston and Porsche. The XKR occupies the ground where GT and sports car overlap, but these rivals are entrenched well inside sports car territory.

It’s the Aston that takes the fight to the Porsche. Compared with the 911, the Vantage Roadster is significantly less practical, much thirstier and a bit slower too. And you know what? None of that matters because it’s unquestionably more glamorous and more desirable.

The 911 Cabriolet is remarkable in that it’s no less practical than the coupe and drives just as brilliantly. And it blends this with a surprisingly good ride, too. We definitely wouldn’t order one in nut brown, though whatever colour it’s painted, the Cabrio is the ugliest 911.

There’s another inescapable fact: it’s the best drivers’ car here. The Aston is engaging and able, but its polish isn’t as deep. It gets close in the dry, but we discovered that it’s a bit of a handful in the wet, even with stability control on. So if it’s the most rewarding drive you’re after, the 911 is where it’s at. You may find, however, that overall your life is enriched more by the Aston.

Comparison