The Mercedes SL is a grand tourer. An example of a smaller car. GT is more to do with drive characteristic i.e. effortlessly covering long distances, which the RC does.
Of course this is all subjective. Having masses of power, or at least far more than can be exploited on UK roads, can be very relaxing or in my experience, frustrating. Hence my choice of the 300h over the RC-F
Unless one is routinely crossing the Continent, the more modestly powered car is much kinder on one's nerves (and license!).