Tseting and developing cars on the nurb is good for when people then take the cars they brought to a race track, but in the real word its sometimes a disadvantage. For example over on a impreza board a guy was complaining saying that the M3 is too hard to drive fast on public roads because it was too bumpy to get power and grip down. He said he would be much faster in a evolution or impreza.

Another advantage also for audi having quattro you can blast off with them on public roads. A evo would still beat a RS4 round a bumpy B road though.