What are the chances of two car manufacturers based in the same city launching cars with the same name, which are direct rivals, some 6000 miles away from said city, yet within 250 miles of each other? On exactly the same day. And both calling their cars ‘GTS’? You’ll think I made it up.

But that’s exactly what happened. Last Wednesday Porsche launched its new 911 GTS to the UK media at the Willow Springs Raceway in California while, four hours to the north the similarly Stuttgart-based Mercedes-Benz were introducing exactly the same media to its new AMG GT S supercar at Laguna Seca in, er, California. Happily I was able to gatecrash the Porsche party a day early which is the only reason I am able to bring you impressions of both having driven each on road and track, 24 hours apart.

I’m hoping you’ll know the basics of each car already but in essence the 911 GTS is the bridge between the normal Carrera S and splendidly abnormal GT3 while the AMG GT looks like an SLS replacement but is in fact far cheaper (like the Porsche, prices start with five figures) and designed to compete not with Lamborghinis and Ferraris, but 911s, Aston V8 Vantages and Audi R8s. The GT comes in standard form with 455bhp from its 4-litre twin turbo V8 at a price of £97,195 while the GT S I drove has 503bhp from the same engine for £110,495. The 911 has only 424bhp but is lighter and yours for £91,098.

I will review the AMG in full in the forthcoming issue of Motor Sport but what would you expect of such cars before you drove them? I’d back the Porsche to be the more hardcore driving machine, the one that would ask the more probing questions of its driver but offer the greater rewards too. The Mercedes would counter by being very fast, making a wonderful noise and besting for Porsche for the boring but important stuff like ride and refinement.

But that’s not how it transpires at all. The 911 GTS, with a little more power and slightly better suspension control, is a fabulous car to drive hard, at least if you choose the two wheel drive coupé version with a much improved manual gearbox. On the mountain roads near Willow Springs and then around this formidable race track it was poised, responsive, quick and, most of all, very easy to drive. It is exactly as described by Porsche and so much better value than the Carrera S upon which it is based I wouldn’t be surprised to see sales of the latter dwindle to a mere trickle.

The AMG is a rather different proposition. With an engine set some distance behind the front axle line and a gearbox between the rear wheels it has an effectively mid-engined configuration and a distinct rearward weight balance. Simple double wishbones suspend each corner. On the track it is simply epic.

I know this because I did 20 laps of Laguna Seca in it, every one of them trying to keep up with four-time DTM and serial sports car winner Bernd Schneider in a similar car. I succeeded only because I don’t think he was trying terribly hard. But by following his lines and braking points around a circuit I’ve not driven for a few years, I was able to concentrate entirely on controlling the car.

It offers five different electronically controlled driving modes though the last ‘race’ mode allows for so much oversteer you’d only see more if you were doing drift practice or about to crash. And it is no toy. On the contrary, this is a hardcore driving machine that can only be tamed either by leaving the electronic safety nets switched on, in which case it will behave like a model citizen, or treating it with a very firm hand indeed. It understeers not at all, offers incredible grip for a car on standard road tyres and, when it slides, commands that you be both quick and accurate with your correction. Its new 4-litre engine is a thundering brute too, its bellowing voice and near instant throttle response belying almost entirely the fact that it is turbocharged.

This then is a car of broad ability and complex character. It’s actually a far harder car to drive fast than the Porsche, but you’ll emerge having had an even richer and I would say more rewarding experience. It is actually the Porsche the counters with a real world argument, offering better ride quality and a far more spacious cabin with at least vestigial rear seats.

Which would I have? It’s actually a fairly simple answer: if you want or need one car to use all the time, it has to be the 911 because it’s easier to live with and considerably so, while still proving a proper driver’s car. But if you already have that base covered by some diesel powered saloon or similar and instead want a junior supercar purely for the thrill of it, a car to drive when you want and not when you don’t, the new AMG GT is an equally clear winner.