Are they supercars? Are they sports cars? Well, who really knows, and who really cares about the semantics; they're both hilariously powerful rear-wheel drive coupes, and we want to know which one would win in a good old game of Top Trumps.

2018 Mercedes-AMG GT R
2018 Porsche 911 GT2 RS: First Drive
Mercedes-AMG GT R
2018 Porsche 911 GT2 RS: First Drive

The cars

The Mercedes-AMG GT R arrived in a lurid green flurry of long bonneted, anti-social V8 savageness, and we love it. It's lairy without being terrifying, precise without being characterless. The Porsche 911 GT2 RS might have a two fewer cylinders, but the evergreen appeal of Porsche's rear-engined sports car is still strong in this bonkers take on the rear-engined icon. We've driven both, and neither is the widow-maker you might be expecting considering the amount of power going to the rear wheels, but here's how they stack up on the figures: 

  Mercedes-AMG GT R Porsche 911 GT2 RS
Price £147,655 £207,506
Engine 3982cc, twin-turbo V8 3,800cc twin-turbo flat six
Transmission Seven-speed dual-clutch auto Seven-speed dual-clutch automatic
Drivetrain Rear-wheel drive Rear-wheel drive
Power 577bhp at 6250rpm 691bhp at 7000rpm
Torque 516lb ft at 1900 - 5500rpm 553lb ft at 2500-4500rpm 
Power to weight 354bhp per tonne 447bhp per tonne
0-62mph 3.6sec 2.8sec
Top speed 198mph 211mph
Fuel economy 24.8mpg 23.9mpg
CO2 emissions 259g/km 269g/km
Seats 2 2
Length 4551mm 4,549mm
Width 2075mm (inc. mirrors) 1978mm (incl. mirrors)
Height 1284mm  1,297mm
Wheelbase 2630mm 2,453mm
Weight 1630kg 1,545kg 
Fuel tank capacity 85 litres 64 litres

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Which one wins? 

Well, it's got to go to the Porsche. Truthfully, this is an unfair fight given the Porsche's much higher price and power output, but in spirit and execution there are a lot of similarities between these two hairy-chested rear-wheel drive coupes. In fact, the AMG GT R held the Nurburgring lap record for rear-wheel drive production cars with a time of 7min 10.9sec, until the Porsche 911 GT2 RS set an astonishing time of 6min 47.3sec. 

But leaving the numbers game aside for a moment, which one looks best and which one would we want on our driveway? Hmm. It'd probably be green. Check out the first drives and the galleries below, and let us know which one you'd have via our Facebook page or tweet us @Motor1UK

Gallery: Mercedes-AMG GT R

Gallery: 2018 Porsche 911 GT2 RS: First Drive