I found the BMW 320i Touring Car a pleasant car for single-model races, including unlocking the 'Ring to S level (and winning too). I haven't tried it in multi-model races, however. Cr400,000 makes it a bargain for a "racemod".
But I expect my favourites to be transitory, and that I'll have a new one a week from now.
I suspect that, because of the awkwardness of the controls and the lack of vibration feedback it will be even more difficult than in previous games to keep proficient at driving different cars at the same time.