[DocWalt]

Ideally you don't want understeer or oversteer. Realistically, line choice and driving style contribute a lot.

edit: figured I'd clarify. The ideal car is one that never slides at the front or rear (ignoring slip angle and all of that fun stuff) but the driver's comfort plays in. Is the driver smooth enough to make a car that's 100% neutral work? Is the driver more comfortable with understeer or oversteer? A small line choice change can compensate for most car behaviors and if the driver is more comfortable they will be faster. Pro drivers are as fast as they are because they can very quickly adapt to a car by changing their cornering a little bit ir tweaking the car to their liking.

It's really interesting to have two people drive the same car and see how differently they approach the goal of going fast. I recently shared my car with a friend of mine that normally drives much faster cars and it was very revealing how differently we drive, some of it habit from different cars, some of it purely preference.