Its a good question, the boundaries between supercars and sports cars in terms of performance are definitely crossing. Supercars however for me are the cars that people dream of, equally awesome to look at as they are to drive. You never look at an SL and really take notice of it and I would imagine that driving one, it would never really make you feel special, although it would be fast, and safe and being german would never break down etc.
Also you could drive it to work every day in comfort, you could park it in Puerto Banus in mid summer for an hour and not get one finger print on it, let alone scratches from jeans of people who think its okay to sit on a car for a holiday photo.
Perhaps the rolls should be reversed and cars like the SL should be called supercars, because they can literally do everything, all of the time. The only thing I would say is that I never had a picture of one on my wall as a kid and still I don't dream of owning one. Even Mercedes' range topping Mclaren tuned SLR lacks the heritage, the looks and out and out supercar driving dynamics of an F430 or the crazy Lambo Murcielago. Real supercars IMO
