It turns out that the 20 more horsepower of the GT over the “regular” version don't seem to make a whole lot of difference, which is somewhat understandable when not directly comparing the two models. The overall experience of driving the GT model isn't something not to yearn for if you have the required depth in your pockets though.
AutoBlog were more than pleased with the un-Earthly sound that the 583 American horsepower (591 in metric hp) M159 V8 makes while the right foot is firmly planted on the go-fast pedal, while the official acceleration figures were consistently backed-up by the AMG Performance Media telemetry system on board.
Speaking of which, this system can part you with $2,500 in the options list, but it's also one of the cheapest features you can add to the $208,000 MSRP starting price for a SLS AMG GT Roadster in the US.
Apart from the usual oohs and aahs in the performance category, the reviewer was also a bit ecstatic about the car's, not necessarily thanks to the good fuel economy of the engine but thanks to the oversized 26.2 gallons fuel tank. You can check out the full review here.