Read about it HERE
Video is mostly about the model S. They brought the Slingshot "because it was the fastest thing they had in the shop." Slingshot is at the 13 minute mark btw.
They also note that launching & driving a sling "is an artform." The Tesla requires nothing from you except your right foot - not even steering in this straight line test.
The model S also costs $150K as equipped here. Still like to see how it does against the Slingshot on the pig Trail or Tail of the Dragon! All the launch controllers wouldn't do much good there and the lumbering weight would slow the car WAY down.