Mercedes-Benz told us that the CLS55 AMG wouldn't be coming our way. We believed them and used an E55 AMG for our megasaloon shootout last issue.

But the first test car delivery to our offices this year was a CLS55 AMG. Surprise!

Finding an M5 wasn't an issue and before anyone could click their fingers, the duo was off to explore perhaps our most exciting face-off of the year. Cars in Action specialises in comparatively reporting on any car, but these monsters are our favourite and a quick look through the archives quickly proved that in nine years, this is our sixteenth comparison test of uber-saloons...

Enough small talk - lets get into the nuts and bolts. Mercedes-Benz hinted at the 'Jaguar Hunter' some years ago - it was considering a sleeker, more performance-oriented sports-saloon to target rivals the like of Jaguar's S-type. Benz research suggested Merc buyers would buy such a thing and early concepts showed a sleek saloon that looked like a coupe with RX8-like suicide rear doors. And it wasn't a pipe dream either and like most Merc concepts, CLS appeared a year or two ago, albeit without those suicide doors.

We first sampled CLS and asked why, exactly it was necessary to offer something like this when there's already a car like the E-class on the market, but Merc drivers clearly enjoy being spoiled for choice and man, CLS certainly makes a statement. Now in AMG form, it really shouts for the more extrovert of Benz bullies...

And while the Benz brass so coyly say this thing targets Jaguar, I'm not so convinced. I reckon its Stuttgart's way of attempting to out-BMW Munich and now that CLS55 AMG is here, the very first thing to do is to pit it against its real rival, right?

So, there we were, cruising out of town in perhaps two of the most provocative cars on the road toady. CLS55 AMG is enough of a thing to encounter on the road all on its own - it presence stirs the emotions of others on the road not unlike a lion's does an impala in the bush.

Pair it with the great M5 and they react to them as if sensing the presence of a lion and a tiger together...

Both of these cars make huge statements. The ultimate Bangle BMW is square, defined, but its argumentative lines question the viewer and with all that M-kit attached, there's no secret that the man in the Porsche had better be sharp. Likewise, the sleek, svelte lines of the CLS are so well defined by that AMG addenda. The Merc's lustrous low roofline so well emphasised by its pillarless glass blends into its sensational and often considered controversial front and rear ends. The AMG kit adequately counters those arguments as well as it wields a stick that even M5 must keep chips on...

And they're luxury limousines on top of it all. Living in the lap of luxury has never been so good - especially for testosterone charged drivers needing nothing less than the absolute ultimate driving reward. They have everything and never mind the kitchen sink; they have huge sledgehammers, too. But it's those hammer-like technical specifications that sets these two so far apart from the rest...

The Merc is graced with the current de-rigueur AMG supercharged 5.5-litre 3-valve SOHC-per-bank V8 lump that is indeed due to be replaced by a new-millennium high-revving 6.3-litre quad-cam 36-valve in the not to distant future. That's something we can't wait to get our sweaty paws onto, which means another re-run of our favourite kind of test to look forward to...

A lump that Kompressor V8 may be, but man, it works! Pumping 350kW and 700Nm through its AMG torque converter auto box, it's fearsome, fast and frightening. But it still can't beat BMW's 5-litre V10 in power delivery - M5 has 373kW on tap, but its 520Nm can't quite match the blown Benz' 700, so the Merc on paper has this one sewn up - especially at altitude, where its supercharger makes up for the drop in ambient air pressure the Beemer has to take on the chin...

M5 bristles with trickery - its fighter jet heads up display, its total dual personality allowing it to switch from being a lazy 400bhp cruiser to a pointed and fierce 500bhp monster configured to your precise transmission, suspension and whatever other needs you have pre-programmed via that otherwise dreadful iDrive at the touch of the little M button on the wheel, is extraordinary.

Both cars are endowed with brilliant performance suspensions with comfort, intermediate and sport settings and both boast beautiful wheels and huge rubber - 18" in the Merc and 19 in the BMW. Look through the spokes and witness the giant cross-drilled disc brakes and ABS assisted multi-pot callipers front and rear. The M5's rotors are particularly big both ends - filling every inch inside those giant wheels and, quite interestingly, dirtying the rear wheels almost as much as the front with carbonised brake pad dust...

The BMW has a trick viscous diff too, which apportions torque left and right not unlike a viscous coupling does front to rear in a trick all-wheel driven car, while M5's F1-like robotized sequential seven-speed gearbox is a sporting driver's dream. But that V10 is a tour de force second to none - is this the ultimate engine on the market today.

So, before we even step into them, the M5 has a technical pedigree to satisfy only the upper extreme of our scorecard. But that does not necessarily mean that it's the fastest, especially at altitude...

Climbing aboard both is as if you're getting into a fat-cat limo. The M5 is now available with a keyless entry system option the Merc has as standard and you can pretty much set them up to do everything for you - auto lights, wipers, mirror darkening and the rest once you get into the cars that unlocked themselves and bore their souls to you on your behalf.

Inside both are also quite different interpretations of a performance theme, although the M5 already certainly seems and feels a little more pointed in that regard. Touch the top of the auto shifter on the CLS and it comes alive in a gruff bark. Snick it into drive, floor it and the world simply blurs as you're punched in the back by immense bottom end torque and thrust. You'd swear you're converting to warp speed it's so immense...

M5 is different, you need to fiddle with the lever to find neutral in that robobox, but fire it up and it utters a rather mechanical tune. Find first with the car bareback in P500 and you're literally driving a F1 car. Unlike the Merc's huge grunt that runs out at six thousand, the M5 only starts rally working there, although it's way beyond adequate until that point.

But from 6000rpm it enters light-speed dimension and dispatches its duty furiously. That V10 screams and the robobox slams through the gears so violently you're wondering when it's going to explode. But it doesn't - it just keeps on pushing you into never-never land...