And that's it. How can anyone choose one from among what must be the most desirable trio of cars on the planet? And yes, perhaps the lesser-known Saab 9-3 Convertible could be added to the list. They represent an art form of gorgeous, dazzling motorised shapes that, like art deco and Bauhaus, could enthral for years to come. It's something the Germans have more to do with than any other country, but more than that, it's to do with the three automobile giants that dream these shapes up.

That said, it should also be remembered that the cabrio segment ? ruled more by the heart than anything else ? is the 'showcase' of the automobile world, and is steeped in more artistic value than other models.

Of the three, the 330Ci is the one beginning to... how should we phrase it... show its age. It also must be said that in terms of shape it did rule the roost for a while before Audi raised the stakes with the A4 Cabrio. The gloriously classic A4?s shape is based on geometric design parameters. Then Merc upped the ante with the all-new CLK with its slick swooping shape, which adds enough zing for the wind-in-your-hair brigade.

The choice is based on sheer elegance and beauty, and on price too. The CLK 320 Cabrio is aimed not at a gap in the market, but at those at the tip of the market. A price tag of R608 000 is testimony to this. That's R100K more than its two rivals. The difference is not solely due to higher spec levels either, that's just part of the answer. Mercs just cost more.

However, don?t forget that the CLK Cabrio chassis is designed to house the monster AMG 55 (5.5-litre) V8 motor. There is a lot of extra strength built into the chassis to take care of those beastly power outputs. When you consider that Merc's Cabrio range in Europe starts with the rather insignificant 4-cylinder 1.8, or even the mid-range 320, this scenario offers peace of mind. The Audi A4 Cabrio series starts with the 1.8T and extends through to the 3-litre V6, while the BMW 3 does the same from the 318Ci to the 330Ci. The CLK is the longest at 4640mm, the A4 the widest at 1780mm, and the Ci the lowest at 1370mm.

Our three protagonists may be beautiful and gracious with the hoods down, but all three look better with them up, in particular the CLK. Just as a beautiful catwalk model looks better without a hat, the same goes for a convertible. But when you add a suitable hat to the mix, a smart chic air is added. It's the same with the cabrio. With the hood up more balance and wholeness of shape is achieved.

Many who are attracted to the open-air driving do not bother overly much about good road holding once they feel the sun on their faces and have their hair blown about in wild abandon. But there is a difference, and it's noticeable when you pilot the Ci. Even with the slight chassis flex and scuttle shake, its manners on the road are impeccable and not too far behind that of its sedan siblings. Scuttle shake on all three is still quite evident, but far less than previous respective models.

On our tight circle test the Ci proved its prowess, especially when traversing the abrupt corrugations, and had far less tyre squeal than the A4 and far less than the CLK. This is tied to its great suspension layout and rear wheel drive, which is also part of the CLK's armoury. However, Merc has opted for a glamorous ride, which is more genteel and structured and goes with the one-with-nature concept. It's also the heaviest of the three at around 1730kg, some 75kg more than the lightweight A4, and this is one of the reasons for its noisier tyre squeal around our test. The A4 fits between the other two with the added weight of its front wheel drive layout offering a slight wallowy effect under hard cornering and rough road surfaces.

Even though the convertibles lack tin-tops they are not lighter than their sedan siblings. The extra flex you get in convertibles due to the lack of a steel roof that offers the extra rigidity causes that old 'scuttle-shake' bugbear. Few makers have managed to overcome this, Porsche being one of the exceptions.

To overcome this, extra bracing and support is added to the chassis, but this is only partly successful. In effect this adds extra weight to the car countering the misconception that cabrios are lighter than sedans.

But, to really stop traffic just lower or erect the soft-tops in any of the Cabrios. With a display equivalent to a Yankee musical dance troupe, it will fascinate and bewilder even a rocket scientist with its array of complex movements that seem to be going nowhere, but end up in two great finale positions. And, its all press-button stuff and so easy to engage!

Cabriolet buyers may not really be interested in the mechanical side of things, but when you're forking out between half-a-million and six hundred thousand bucks its good to know what you're getting. Petrol-heads will tell you that the V6 quad-cam 5-valve per cylinder is the most advanced of the three, and they're right. Being a straight-6 the Bee-Emm engine is one of the last of its kind found in any sports sedan and is in need of replacement. A great and wonderful engine for more years than one can care to remember, the quadcam V6s have now usurped it in compactness and future development potential. The Merc V6 is okay, but being only a SOHC with 3-valve combustion chamber layout it lags behind in high tech terms on the Audi.

When it comes to performance, it is the 330 Ci that dominates, the engine informing you of its intentions with that glorious, though subtle, exhaust note even with the hood up. The Merc holds a strong second spot.

However, the big feature during testing was the A4's Multitronic, continuously variable, automatic box that takes motoring comfort to new levels. Yes, I was blown away by the gearless, seamless smoothness through the range. Neither the Ci nor CLK can match this with their oil-based multi-geared automatics.

From the moment I slipped behind the wheel of the CLK with the sun bathing that glorious interior I was sold. The metallic inserts on the dash and doors knocks the dour Germanic feel of the Ci and A4, they're simply not in the same league. Their straight-up-and-down corporate look is starting to wear thin. Yes, it does present an orderly, precise look, but it's boring.

In the end it's not the many minor differences and variances mentioned above that sway cabrio buyers from one car to another. At this level it's more to do with style, recreation and gratification than the objectives needed when purchasing a car for everyday use. The designers of these beauties know the goals they are chasing well! These are the showcase models of each maker, designed to offer the best in diversion, comfort, and create that wonderful altered state of mind a good movie can create.

Cabrios are also cars that can be bought on a whim. Any art collector is imbibed with the basics, but the difference with a cabrio is that this art form can be driven around for everyone to see and enjoy, including its wind-in-the-hair driver.