For an endurance race the speed isn't the only thing. How it handles tyre wear and drinks fuel can be more important.
If the tyre wear ratio is high, then maybe something like the Cayman or the GT86 might be good, but if fuel is important then maybe Mitsubishi Lancer might be a good option.
Saying that, the Megane and the Audi TT will both be very strong over 1 lap. Up to you at the end of the day
For some reason I love the Veyron. It demolished everything on the straight and has excellent grip so you won’t need to worry too much about tire wear,