I chose the Miata, and was very pleased. It allowed me to race a numer of series and win a bunch of cars before I had to start upgrading other cars.
It's good for the FR, The Sportster/ Roadster, The Turbo (If you Turbo it), and the 80's, as well as the first two. You will win a trueno and a Vitz, and a lightweight car pretty soon too anyways.