Those in the fortunate position to be eyeing up a new four-door saloon with a V8 engine are rather spoilt for choice at the moment. This pair aren't even the only offerings in their respective ranges - there is a Panamera Turbo S and an M550i bookending both. That's before considering Audi (RS7) or Mercedes (E63, GT63). There are Alpinas, too, and the Bentley Flying Spur V8 is more than worthy of consideration for those with a bit more to spend. The world might be fast electrifying, but there's a little enclave of super saloon silliness that's still gratifyingly well populated.
It's been a very long time since a Panamera GTS was reviewed on PH. There's no particular reason for that, though it's possible we can chalk it up to other models in the range hogging the limelight. In other Porsches, the GTS tends to be a nicely struck compromise between handling prowess and outright performance; in the Panamera, the powerfully built saloon for powerfully built types, it's very easy to see the lure of a 630hp Turbo S. When opting for the Porsche flagship, why skimp, right?
Like the 530hp BMW M550i, it's quite incredible that a 186mph GTS is the diet performance Panamera, but such is the power-hungry world we live in. In addition, it takes all of about 10 minutes to question the need - as in pretty much every other Porsche GTS, actually - for any more Panamera than this. Or any more car, period. It's uncannily excellent.
Everything in the Panamera works with such clarity and precision that it makes everything else seem almost botched. And that's not just the driving side of things, either; it's the way every button, switch and handles operates, the slickness of the infotainment, the seamlessness of everything the driver is required to interact with. For a car launched five years ago - though updated very recently - the Panamera remains a masterclass inside. Crucially, too, the GTS subtly improves on that base, even if that effect is mostly achieved through a sports steering wheel and the application of Alcantara.
On the road, initial impressions are understandably dominated by the powertrain. The 4.0-litre V8 is rich and emotive in a way few engines now are, its cylinder layout never in doubt but never overbearing, either. It rumbles and burbles and thunders along like all the best V8s should, authentically impressive even if the noise is manipulated a touch. Once the turbos have readied themselves, performance is strong and consistent, building to a peak just before the redline and another gear ratio flashes through the flawless PDK transmission. The GTS never threatens to blow you away with its performance, but it's not that sort of car. It is amply fast, and sounds like distant NASCAR - that ought to be enough for most.
Like most contemporary makers of sports cars, Porsche can occasionally be accused of prioritising grip over feel and outright performance over driver satisfaction, and the same is largely true here - though it matters less in a five-metre, two-tonne saloon. Instead, you tend to marvel at how something so large and so heavy - with a few carefully chosen options - can be this accurate, this incisive and this ruthlessly well controlled. There simply isn't a situation that flusters the GTS, with immense cornering speed and traction regardless of what's beneath it. That it does so while still giving the driver just a bit back - the weighting and precision of pedals and steering see to that - again complement its omniscient character. If you're inclined to ask why anyone would consider the GTS when there's a Turbo around, rest assured the roles are very much reversed after time spent behind the wheel. Consider it an expertly prepared three-course meal; what might not look all that much given what you're used to somehow leaves you perfectly sated, not craving one bit more or anything less, either.
It'll probably come as no great shock that the BMW represents a rather different sort of dinner. If the Porsche is a model of restraint, the BMW is more overt; perhaps not on the outside, where gold calipers are the only real give away of intent, but most certainly inside, where the attempts to impress with myriad buttons and screens and a joystick for a gearlever look a bit OTT. BMW interiors are typically very nice - and lots here is great, including the driving position - but it takes second place behind the GTS.
To understand how different these cars are to drive, consider the tyre sizes. Both share a chunky 275-profile section front (Pirelli P Zero for the BMW, Michelin Pilot Sport 4S on the Porsche); but whereas the Panamera has an enormous 315-section rear, the M5 makes do with a 285. With another 145hp. And near enough an extra 100lb ft...
So while the Panamera is tirelessly composed and indefatigably grippy, the M5 is a tad friskier. Not in a dangerous or silly way - it's still possible to make very rapid progress well within its limits - but in a fashion that makes it that bit more interactive to drive. Like all the current M cars, so much rubber on the front means it dives for an apex very confidently, meaning you tend to think about the exit of a bend almost as soon as the car is turned in. And where the all-wheel-drive Porsche seldom hints at its rear-biased hardware, the BMW is pretty unabashed, messages through the wheel and seat telling you this is most certainly an M car, four-wheel drive or otherwise. Which is nice. 4WD Sport, often forgotten in the hype around 2WD mayhem, is the really clever mode.
Typically BMW's 4.4-litre V8 gets some stick for sounding a bit flat, and that remains true here, but the performance is undeniably monstrous. Driven back-to-back the real surprise is finding less turbo lag in the M5, and a tad more willingness at the top end as well, really revving out past 7,000 where the Porsche feels like its 6,800rpm limit could be lower still. BMW has had a long time to get the most from this engine, and it shows; by comparison, the GTS V8 can feel a little stifled, hemmed in as it is by range hierarchy.
Like the new M3, the M5 uses a conventional automatic gearbox; as in that car, it's hard to find much fault with unless driving like it's a DTM race. In fact, given an M5 is now a six-figure luxury car as much as anything else, an automatic is a perfect fit, easygoing when required and more than responsive enough when needed. Sure, the Porsche's transmission is marginally better when you really go looking for it, but precious few will appreciated the difference.
There's another trait the M5 shares with its little brother, and it's a less positive commonality. Making big, heavy cars this exciting to drive comes with a price, and it's the ride. Where the Panamera's air suspension can be left in Comfort or Sport (but not Sport Plus) without giving it a second thought, the BMW only ever needs Comfort. Even then it fidgets at lower speed more than the GTS, before becoming equally imperious at cruising speed. Does it matter? It certainly seems worth pointing out; those after an M2 or M3 are likely a different customer to an M5 buyer, more willing to endure a bristling ride for handling edge. In a £120k car the concession seems less reasonable. BMW says this the ride of this Comp is more forgiving than the last, with dampers from the M8, but be under no illusion: this is a resoundingly stiff car.
All of which makes deciding between it and the GTS fiendishly difficult. Because on the one hand is perhaps the most accomplished sports saloon this money can buy (we'll know for certain after trying the new E63), a dazzling display of engineering aptitude and Porsche-honed finesse, topped with a rather splendid V8 engine. On the other is an immensely likeable hot rod of a 5 Series, a car that doubles down on the idea that a little too much power is probably just enough and thrills you in a way the more measured Panamera could never dream of.
As a luxury car with a sporting edge, i.e. something to gratify both driver and passenger, any time and any place, the GTS is superior and arguably the pick of its own absurdly talented lineup. But as something to really drive, selfishly and without moderation, the M5 is the car to go for. At virtually every turn it reminds you why a V8-powered saloon is still regarded in some parts of the world as the pinnacle of automotive pleasure-giving. Let's all hope that the wider niche continues in its rich vein of form for a little while longer yet.
SPECIFICATION | PORSCHE PANAMERA GTS
Engine: 3,996cc, twin-turbo V8
Transmission: 8-speed PDK dual-clutch, all-wheel drive
Power (hp): 480@6,500rpm
Torque (lb ft): 457@1,800-4,500rpm
0-62mph: 3.9 seconds
Top speed: 186mph
Weight: 2,020kg (DIN, without driver)
MPG: 25.9-26.4
CO2: 244-249g/km
Price: £107,180 (price as standard; price as tested £120,670 comprised of USB interface in rear for £125, BOSE Surround Sound System for £1,062, Sport Chrono stopwatch instrument dial in Crayon for £260, ISOFIX child seat mounting points on front passenger seat for £134, Seat heating (rear) for £366, Ambience lighting with rear compartment interior lighting concept for £581, Ioniser for £215, 4+1 seats for £626, Soft close doors for £545, ParkAssist including Surround View for £635, Privacy glass for £389, Tinted LED main headlights with matrix beam including Porsche Dynamic Light System Plus for £1,166, 21-inch Panamera SportDesign wheels painted in high gloss black for £1,215, Rear-axle steering including Power Steering Plus for £1,563, GTS interior package in Crayon for £1,938 and Crayon paint for £2,670.)
SPECIFICATION | BMW M5 COMPETITION
Engine: 4,395cc, V8, twin-turbocharged
Transmission: 8-speed auto, all-wheel drive
Power (hp): 625@6,000rpm
Torque (lb ft): 553@1,800-5,800rpm
0-62mph: 3.3 seconds
Top speed: 190mph
Weight: 1,950kg
MPG: 26.1
CO2: 246g/km
Price: £102,323 (price as tested: £118,560 with Ultimate Pack)
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