What will they cost?

It isn’t often that a BMW turns out to be the cheap option, but in this company, the 6 Series is just that. In fact, it’s around a third cheaper than the Porsche Panamera, which is a pretty significant chunk of money.

And while the Porsche will hold its value better in percentage terms, the chances are you’ll lose no more hard cash on the BMW over the same time frame than you will on the Porsche – or possibly even slightly less – simply because it’s starting from a lower price in the first place.

Given the mightiness of its performance, it’s all the more impressive that the BMW emits just 148g/km of CO2, which means it will cost you a not-unreasonable £150 a year to tax. The Porsche, by comparison, with its 172g/km emissions, will set you back £220 a year.

The trend follows through to fuel consumption, too, where the BMW’s official average figure of 50.4mpg rather trounces the Porsche’s 43.5mpg. In the real world, the chasm between those two figures reduces, but it’s still the 6 Series that has the edge.

And in terms of servicing, the BMW once again comes out the cheapest. You’ll pay £295 to have a minor service carried out on your 6 Series 640d Gran Coupé at a BMW main dealer, or £465 for a major service; by contrast, the Porsche will set you back £455 for a minor service, or £555 for a major service.

It’s hard to find specific reliability data for either of these cars, but both manufacturers have a less-than-exemplary reputation for reliability, with both having received below-average scores in the What Car? Reliability Index. However, of the two, it’s once again the BMW that looks like it’ll hurt your wallet the least, with a slightly better rating, not to mention lower repair costs.