If you fancy 616bhp (precisely), then as from today you have the choice of two cars – McLaren’s 12C or Bentley’s Continental GT Speed. Yet despite their identical power outputs, they couldn’t be more different.

The 12C is strictly a two-seater, whereas the GT Speed can accommodate four. The two-wheel drive 12C could prove a little tricky on slippery roads, whereas the GT Speed comes with the reassurance of a full set of driven wheels. The 12C will set you back £178,500 compared to £160,000 for the GT Speed.

But perhaps the most telling difference is their weight – 1,434kg for the McLaren and 2,320kg for the Bentley. They really couldn’t be any more different could they?

Bentley needn’t fear losing custom to McLaren (and vice versa), there are plenty of wealthy people who, if forced to make a decision, would probably choose both. And that’s the strange juxtaposition in these challenging economic times – while George Osborne struggles to balance the UK government’s books, Bentley Motors’ CFO Jan-Henrik Lafrentz has seen global sales for the first half of 2012 increase by 32%.

Business is booming in the luxury car sector and Bentley is making hay while the sun shines.

The arrival of Bentley’s 205 mph all-wheel drive performance flagship coincides with a new engine management system and eight-speed transmission being fitted to all W12-engined Continentals.

In the 567bhp Continental GT coupe and GTC convertible models, this delivers a 12% improvement in fuel economy and CO2 emissions – or a 10% improvement for the GTC W12. With the new eight-speed transmission delivering 6% of the total efficiency gain.

The new ZF eight-speed transmission is designed to handle the W12’s high levels of torque, cutting acceleration times by ensuring the engine is always at the ideal speed for peak torque delivery. This innovative transmission also features “Block Shifting” technology, which means it’s capable of shifting directly from 8th gear to 4th gear (for example) for instantaneous response and thunderous acceleration.

Acceleration from 0-60mph has been reduced by 0.1 seconds to 4.3 seconds in the 567bhp GT, while the GTC’s time drops by 0.3 seconds to 4.4 seconds. 100mph is now reached from standstill in 9.8 seconds for the coupe and 10.3 seconds for the convertible.

Let’s not get too excited though by the 10-12% drop in fuel economy and emissions – the W12 GT improves from 17.1mpg to 19.5mpg with CO2 emissions of 338g/km (down from 384g/km), while the GTC delivers 19.0 mpg and CO2 emissions of 347 g/km. Bentley claim the same fuel economy and emissions for the GT Speed and GT W12, despite the flagship model’s extra 49bhp and 74lb-ft of torque (590 lb-ft vs 516 lb-ft).

The new GT Speed will make its official international show debut at the Moscow Motor Show on 29th August, although orders are being taken now with deliveries scheduled to begin in October 2012.