An interesting interview (in English) with GT3 driver David Perel, on his journey into GT3 racing, the dollars, and driving real life and sims. Regarding sims, he says real life driving style is much more aggressive than in sims. You are always doing moves which would be considered "dirty" moves in sim racing. He also says that in general sims don't get the braking right. The real life feel of how a car rotates and the feedback you get via the brake pedal is not simulated very well.
Interestingly, he says that in GT3 racing, you take a "V" line while braking. Brake very hard, nearly stop to let the car rotate, then get hard on the power. It's no wonder so many sim racers complain about understeer. They're just coming in too fast and trying to maintain too much corner speed.