Much the same can be said of BMW's Compact 320td SE auto which endured a rather uninspired first incarnation, but has blossomed in its second coming into the top quality drivers' car users expect from BMW.
The Peugeot 406 Coupe, too, has been held triumphantly aloft since its launch.
The svelte Pininfarina body is Ferrari style for high street prices, with tried and trusted mechanicals. But while it might stack up well against Peugeot's usual foes, this time it is placed against premium sector giants. Expect blood and tears somewhere by the end.
Pricewise, the Mercedes Sports Coupe is more expensive than the BMW by more than £2,000 at £24,120 - but better emissions than the Compact level the two out when it comes to personal tax liability.
But the taxable value for the 406 is cheaper at about £900 less than the Germans, which for a 40% tax payer is a saving of about £350 a year, even before cheaper fuel costs kick in.
The BMW is the cheapest here in terms of P11D value at £21,950, but bear in mind that just to add body coloured door handles costs £95 extra, and it would not be long before a couple of injudicious ticks on the options list sent the price soaring way past the 406, which costs slightly more at £22,120.
As for monthly rental rates, the gap is much closer because the three-year/60,000-mile residual value forecast for the Mercedes-Benz and the BMW are typically as solid as the walls of Windsor Castle at 41% and 43% respectively, according to CAP Monitor.
The 406 is more sandcastle, retaining just 30% of its value over the same operating cycle, which is a surprisingly small amount for a car that seems to be so desirable. This is cancelled out to a certain extent though by cheaper service, maintenance and repair costs of 2.91pence per mile, compared to 3.83ppm for the 3-series and 3.79ppm for the Sports Coupe.
No real surprise there, as running a premium marque such a BMW or Mercedes-Benz means paying a premium labour rate.
In terms of fuel consumption, the Peugeot wins hands down, reaching 44.1mpg on the combined cycle, with the Mercedes a couple of miles back at 42.2mpg and the Compact lagging at 40.9.
However, it is worth remembering that the 406 is only available with a manual gearbox which helps it in this case.
Such is my dedication to the fleet cause that I laid awake at night pondering which of these three cars I would choose, because not one really stands out as being better or worse than the others.
The Sports Coupe and Compact are classy, would look lovely on the driveway, and impress the neighbours, although the BMW is the better driver's car, and has marginally better resale value.
The 406 is the bean counter's favourite. It is less heavy on tax, better on fuel and cheaper to service. But it is older and has comparitively appalling residuals.
As a fleet manager who does not have to deal with its resale, I would be keen to persuade drivers to take the 406. But I'm not, and as a driver, and one carrying around the psychological baggage of wanting to impress friends and look cool, the £350 a year saving is not enough of an incentive to choose the 406 against such esteemed marques as BMW and Mercedes-Benz. As the sun rose, I tried to prise the Sports Coupe and Compact apart, and in the end the BMW won because our test Sport Coupe was not screwed together very well, is less fun to drive and BMW's diesel engines are much more refined. Time for a nap, I think.
The Sports Coupe is one of those things, like olives or gardening, that I cannot decide if I like or not.
I wander up to the front of the car, all low, wide and muscular and think everything that is good about Mercedes cars is distilled in the nose: manly grille, lights like splashes of mercury and a louvered bonnet. A steeply raked window and dynamic flanks add to the appeal.
But round the back the glass boot lid/glass and lights concoction is a mess. The whole thing is so overly fussy and so unlike Mercedes' typical composed elegance.
To the interior, and the same conflict. The dash looks good, in the same way as the C-class does: a slighter, more swoopy interpretation of the blocky, humourless Mercedes interior that has served the company well for so long.
The multi-function steering wheel is superb, echoing an upside down pointed star, and the seating position is unusual but once worked out, proves extremely comfortable.
You have to sit low and straight legged, with the whole sole of your right foot resting against the floor-hinged accelerator pedal, like in a TVR.
Great stereo, and all the functions clear and simple to use. What could be wrong with this car?
For one, some of the plastics are far too cheap and flimsy for a car of this price, and over bumps, the dash squeaked and rattled. A Mercedes that squeaks and rattles! Another annoyance is that the rear window has no wiper.
And then I'm not so keen on the engine. The 2.2-litre common rail direct injection diesel engine is clattery and takes a long time to get wound up, which coupled to an automatic gearbox makes it more slow coupe that sports coupe, taking more than 10 seconds to get to 60mph. The constant blinking of the traction control light shows there is a lot of torque trying to escape through the back wheels though.
Disconnected-feeling steering does not do the decently sharp rear wheel drive chassis justice either.