The battle lines have been drawn. They run like China's Great Wall through a set of performance figures, demarcating winners and losers in a game that is oft confined to barroom talk.
In this game, BMW's brand new Z4 M Coupe' indeed shades the opposition.
It is superior to Porsche's Cayman S, for instance, in the 0-100 km/h dash.
In fact, Mr Coup beats Mr Cay by almost half a second - 5.0 vs 5.4 secs - lugging more weight around, using less cubic capacity.
The Beemer also develops more peak power and torque than the Porsche, albeit at higher revs.
Which is impressive. But any aficionado will tell you that straight-line whoopies are but a small part of a roadster or coupe's total package of fun.
What really flips the pancake is an ability to change direction.
Tracks and twisties
On to the twisties then.
For it is only in this kind of environment that all the qualities demanded from a sports car will be put to the test: steering, grip, traction, engine response, in-gear acceleration, the box itself, body control, balance, brakes and so forth.
Apart from timing your blitz through the gears or measuring disc sizes and braking distances, it is hard to put objective figures on any of these.
For the record, the Z4 M Coupe' carries significantly larger front and rear brake discs than the Cayman S.
It also registers a torsional rigidity of 32 000 Nm/degree, whereas 31 500 Nm will be enough to twist the Cayman's body through a single degree.
Not much of a difference in an oft-neglected statistic, granted.
But it confirms that BMW has pulled out all the stops on the Z4 M Coupe'. This is one very serious sports car, from letting a lot of horses run wild, to limiting body flex with Gestapo-like control.
The Z4 M Coupe' is, in fact, such a serious car that Munich expects a lot of them to be snapped up by track enthusiasts.
That's part then, of the reason that we're here, on Circuito Estoril, west of Lisbon on Portugal's Atlantic coast, with a BMW specialist leading the way in a M5, to show us the ins and outs of a technically very demanding circuit.
Even on the opening lap, the M5 is pushed to its limits and beyond, the big bruiser running side-ways through a number of corners.
The M Coupe', by contrast, hangs on with remarkable ease.
After two laps the M5 peels off. It's you, the M Coup and Estoril, all on your own.
Now, with Coup's 252 kW/7 900 r/min spewing forth from a multiple award-winning 3.2-litre straight-6, real top-end velocity will clearly shatter the electronically limited 250 km/h imposed by BMW as part of a gentleman's agreement with Merc and Audi.
Porsche not being part of this pact leaves the Cayman free, of course, to push the envelope out to 274 km/h.
But a few choice words in your best Don Corleone whisper will surely be enough to de-restrict a chip or two in your Z4's engine management programme - governed, as it is, by a 32-bit micro-controller with two additional timing co-processors capable of 64 million instructions per second.
In the process Munich's high-speed power unit - revving freely and lustily to 8000 rpm - runs the pistons at a speed of more than 24 metres per second; just less than a F1 car's piston speed of 25 metres per second (a figure which is, incidentally, matched by the 4.2-litre V8 in Audi's potent new RS4).
Part of the secret ?of a plant that has now been crowned as ?Best Engine in the World for the 3.0- to 4.0-litre segment? six times in a row, is race-reflecting technologies like individual butterflies for each cylinder.
Being electronically controlled - whilst system related data (like gas pedal position) are evaluated no less than 200 times per second - these throttle butterflies are continually adjusted for optimal performance.
At flat out speeds this means opening them to the max in just 120 milliseconds.
Other BMW-specific jewels comprise of a light-alloy single-piece four-valve cylinder head, variable double-VANOS camshaft management, graphite-coated cast aluminium pistons with machined piston crowns, forged-steel pre-cracked conrods and a crankcase made of hight-strength perlite casting.
Amongst others, this also serves as the foundation to a wrenchingly torquey 365 Nm/4 900 r/min - with 80% thereof already available at 2 000 r/min.
So, if your best Mafia impersonation fails to get the 3.2-litre straight-6 de-restricted, a tiny fraction of this twist - primarily exerted on a mechanic's arm - might do the trick.
Gearbox and clutch
A good deal of such stonking stomp will, however, go to waste if the gearbox happened to be sub-standard.
But drive an old BMW 2002ti, for instance, and it's clear that the DNA of cog-swopping units with short, swift and positively precise shifts imbedded in a wholesomely healthy box has been structured a long time ago.
The M's clutch could be jerky, yes, if depressed too late or the pedal released too far.
In contrast though, to the Sport Button - which speeds up the throttle and really results in snatchy take-ups - soiled gear changes actually amount to sloppy driving, period.
In the manner then of so many other chassis and suspension components, including the M differential lock, the Coup's box is carried over from BMW's potent M3 sports saloon.
That also makes the M Coupe' pretty similar to the M Roadster.
But in reality the cars differ quite a bit, even in terms of hardware.
Brakes and suspension
The first major change over the M3 saloon is upgraded brakes for the Z4 M models, in the shape of the M3 CSL's 18-inch compound system that viciously slashes speed to the bone.
The M Coupe' also boasts a number of small, but extremely positive upgrades over and above the M Roadster - like stiffer springs, revalved shocks, a thicker rear anti-roll bar and a quicker steering rack (with a reduced ratio of 12.8:1, compared to the Roadster's 13.7:1).
All of this adds up to a telling difference, especially in the way the tin top deals with road shocks whilst maintaining complete body composure.
The Coup also turns in with more alacrity and precision, and corners flatter.
The end result is a wonderful bouquet of qualities, perfectly suited to hard, focused and uncompromising driving.
All of this yields a lap time around the Nurburgring's Nordschleife that will beat the M Roadster's 8 minutes 15 seconds by at least five seconds, BMW reckons - which will catapult the M Coupe' right up into Cayman S territory.
Of course, track lap times are dependant on a number of variables, like weather, temperature, track conditions, traffic, tyres and last but not least, the caliber of driver and how familiar he or she is with the car and track itself.
So, 'Ring times are not the be all and end all of sports car abilities.
But it is an indicator, just as the M Coup's prowess around Estoril signifies a none too ordinary carriage.
Most cars, see, feel pretty slow around a track.
By contrast, the Z4 is devastatingly fast around Estoril.
Even so, track racing remains a specific kettle of fish. It's a technical battle against the given; with this sort of set-up, speed, turn-in and grip, those are the braking points, apexes and exits, so much the better to be tackled in these gears, with that kind of steering input and just so much throttle, etcetera, etcetera.
Not easy to perfect, of course. But all very scientific, in essence.
And repetitive, which always harbours the danger of boredom.
A couple of hard laps around Estoril is good then, to reveal the character and prowess of the M Coupe': a tendency to oversteer pitted against DSC's ability to sublimate the tail, powerful brakes repeatedly hauling the M down from great speeds without a hint of fade, great acceleration building up to vast speeds, things like that.
Soul and personality
It is brutal, of course, all these extremes. One can murder this car.
But you won't kill it; the Z4's integrity is beyond doubt.
To discover its personality though - the M soul - it's gotta be off to B-roads around Cascais, on Portugal's Atlantic coast, west of Lisbon.
For it is in such surroundings, on roads that weave and wind, twist and turn, snake and curl and rise and dip that the Coup changes from an instrument of assault to an object of pure joy, not to mention desire.
The driving is still fast and aggressive, and corners are still tackled with gusto and enthusiasm.
But the subtleties and rewards of improvisation now take precedence over the gladiatorial need to subjugate.
This is hard but good-natured jostling, rather than veni, vedi, veci.
In fact, vehicle and via interact so intimately, that they morph into two sides of the same coin. They are there for each other, as partners; not pitted against each other, as foes.
And if the M Coupe' is mighty and merciless around Estoril, it is staggeringly supreme in the real world.
The genes are good, of course. Z4 M models are born from the basic Z4, already boasting all the necessary prerequisites for great dynamics, like a long wheelbase and wide stance with a near 50/50 weight distribution on a competent chassis, hurled along by Munich's original 3.0-litre straight-6 masterpiece.
With even more power, wider rubber and a stiffer suspension, the M models were bound to be better, especially as the tyres are not run-flats either.
In reality though, they are not only better, but a helluva' lot better, for the simple reason that M models discard with the standard-Z4's electrically supported power steering in favour of a classic hydaulic system.
Now, forget about BMW's arguments that the electric system is cheaper and easier to install, and that it saves on fuel consumption. That might be true, and it might be relevant on cheaper cars.
But it was a mistake by Munich to use electrical steering at all, let alone on a sports car, simply because such systems are overly light, even in Sport mode, and completely devoid of feeling and feedback.
The Z4 thus steers with the assurance of a computer game gadget.
The two M models, by contrast, offer feel and feedback by the bucket full.
Suddenly, one knows exactly what the state of interaction between the front wheels and road surface is, and therefore how much turn and grip would still be available at any given point.
So, attack remains the name of the game, but the spirit and purpose differs vastly from going to war on a track.
Ditto for the results; in the real world the M shows a far more refined side, compared to its brutal on-track demeanour.
Especially enthralling is the car's willingness to provoke a tinge of oversteer from the tail, when turned in under hard braking.
With some nifty, deft touches on the steering wheel all of this is counter-balanced and co-axed, of course, into a short, sharp four-wheel drift - but only for a moment, before it's back to utilizing copious amounts of feedback through the fingers and pants to target the apex, followed but long joyful tail-slides on the exit.
On the surface of it all, it is brawny and brash, irreverant and bold, lusty and raucous.
Yet mechanically it is so sound and sonorous that, beyond it all, the M Coupe' is really a two-in-one, with ever-so-sweet intestines hidden behind a thoroughly rumbustious personality.
So perfectly are the two integrated, though, that one would never tell.
Brutal M diff
This is a sublime car then, if not entirely sophisticated.
On the edge of performance, the M could even be brutal, as evidenced by a tail happy to be thrown around like a rag doll.
And here-in lies the second big secret of Z4 M models, compared to the standard issue: the M3's variable engine-speed sensing M differential lock on the rear axle, ensuring optimal traction under all conditions.
Hang the Coup's tail out then, with a quick spurt of throttle adrenaline in a traffic circle, followed by a fish-tail of reverse swing out of the exit, and you can literally feel the M diff throwing power around from one tractable wheel to the other.
A very useful piece of engineering then, this trick diff - perhaps not clever enough to beat Bobby Fischer at a game of chess, but crafty enough to teach Houdini a trick or two.
Now, imagine all of this enveloped in a taut, muscular sculpture radiating with testosterone.
Imagine the power under such a wide elongated hood.
Imagine being seated in a snug little cabin on the rear axle of such a sharply truncated, guillotined-off tail.
Man, heads will indeed roll, as it's rolling thunder from four blazing pipes bellowing with a hoarse roar that quickly builds to a 8000 rpm scream.
Add now, the short flick of a gearshift coated in honey and those long, swoopy powerslides, easy as an eagle, if not quite as graceful.
Enough to match - or even trump - the Cayman?
The Beemer is a brute, the Porsche refined; the Coup more canine-like, the Cayman more of a cat.
So, think what you want.
But it all points to a great slugfest if these two ever happen to meet on - or perhaps in - the 'Ring, rather than just your common old barroom.
The Z4 Coupe' range will be available in South Africa from September onwards, and sell at R460 000 for the Coupe' 3.0si and R530 000 for the M Coupe'.