what is the best racing car???
In what series? You can't just ask what the "best" race car is, there's tons of different types. Overall I'd say a F1 car is the "best" but a F1 car would never win in a drag race against a Top Fuel dragster. So we gotta know what kind of race car we're talking about here.
Well then I suppose a Top Fuel. I can't think of anything faster when it comes to 1/4 mile racing.