I really really like the Oreca Viper. It's got great handling dynamics, it's reasonable on tires, and it looks great. A lot of people like the C5R, but I do NOT like it at all. It uses up its front tires very quickly, and once it does, it plows like a barge.
The TS020 road car is going to be quick and light. But I'd go for the Oreca Viper. What are you using it for?