The Porsche 911 Carrera S PDK versus the BMW i8

Simply starting these two up shows the different approaches. The Porsche growls vigorously into life, it’s flat-six 3.0-litre making one of the most iconic of sounds. Push the starter button on the i8 and you’re rewarded with total silence.

It will start in default Comfort mode, and you whisper forward until the electronics decide that you need a combination of 129bhp electric motor and 228bhp three-pot petrol engine. If you keep in E-drive then you’re running just on batteries and you’ll get maybe 15 miles out of it. Put it in Sports mode and it gets a lot sportier.

Get the two working together – and the i8 will decide what it wants to do based on best economy for the inputs – and you’re going to be accelerating really hard. A 0-62mph time of 4.7sec indicates how hard. There’s that delightful thrust from nowhere that the electric motor brings to the party, giving the effect of bottomless torque.

The 911 lets you know it’s working, but initially it’s slower off the line than the i8. However, give it just a few seconds and it’s really into its stride. The Porsche will pass the BMW before they’ve even reached 62mph, with the 911’s time of 3.5sec showing the pace.

Once it is rolling and barking and howling, the 911 can hurtle round corners with a handling package that is simply sublime. The front stays anchored, the back provides slingshot power and the steering is telepathic. Admittedly we had the PASM adaptive suspension, which is a £1133 option, but there’s no question bumps get absorbed well, adding a decent ride to the impeccable handling.

The BMW is perhaps hampered by big 20in alloys, but the effect is much rougher than in the Porsche, with the i8 banging and thumping over road imperfections in a thoroughly intrusive way. At first, this may not be noticed as the i8’s cabin most definitely has the wow-factor. There are blue lights, swoopy designs and it all looks as futuristic as the exterior. Add in the iDrive, simply the best infotainment system out there, and it looks really good. Then you start noticing that the quality isn’t that amazing, looking just like cheaper cars in the range. That takes the blue gloss off a bit.

The Porsche is more traditional and is beautifully put together with lovely attention to detail. It looks a bit dated in the infotainment area, and there are rather a lot of buttons and knobs, but you are in no doubt what sort of cabin this is. You’ll be comfy enough too, although anyone in the back won’t be.

That applies to the i8 too, where rear space is at a premium while front space is excellent and very adaptable. Neither car can take four in comfort for very far and neither can carry much luggage – that may not come as the surprise of the year.

If you’re looking at list prices, then it’s surprising how much cheaper the Porsche is. About £15,000 less for a 911? Both should depreciate at about the same rate, although obviously it’s only the i8 which will get the government grant of, currently, £4500. And it’s the i8 which will cost less to run, although you’d have to be Mr Optimist to believe BMW’s figure of 134.5mpg.

In the unlikely event that you had an i8 as a company car, its very low emissions would mean over three years it would cost about £20,000 less in company car tax than the Porsche, and that’s not chicken-feed, particularly when added to the saving in road tax - £620 over three years instead of the Porsche’s £2620.

As a vehicle, the BMW i8 is quite something. However, if you bought one of the BMWs you would not be able to say, in text-speak that ‘i8 a Porsche 911’. The i8 is gorgeous to look at, and has very low running costs, while setting out your green credentials. It also is very easy to drive.

But these are sports cars, and that means thrilling driving, handling and much else besides. On that scale it can only be the Porsche 911 Carrera S that takes the honours. It handles so incredibly well, goes and sounds like nothing else, and is even a comfortable ride. And with a five-figure saving over the BMW, that seals the deal.