I have 2000km online with the veyron... Itis useless for races, because you just crash every 30 seconds. It is amazing for jumping, speedtests, and challenges, however. Just because of the acceleration..
The Ultimate speed pack is coming out soon, so those cars will be veeeeery much up in the top cars. But before they come.
Any car class races: SRT Viper, Audi R8, Marussia B2, Koenigsegg Agera R, Pagani Huayra, and Mclaren Mp4-12c. They're all good cars that don't crash too often, and pass Bugattis alot, because they always crash. The Viper is the best muscle car by far, the R8 and Marussia are the best sports cars, (don't judge them when they're stock) The Koenigsegg is almost as fast as the bugatti but has more controll and is harder to crash. The Pagani and Mclaren have great handling, so they get round the track well..
For everyday, it's either the Subaru or the AUdi. They're both amazing.
Exotics, the Koenigsegg.
Race, Ariel Atom. it's greeeeeaaaatt.
Sports, the Audi or Marussia.
Muscle, Viper. Manouverable and fast.
Grand Tourers, Bentley Continental. It's fast, and strong.
SUV, the Ford Raptor... Easy decision.
You don't have to be in the fastest car to win. It SHOULD be fastish, but not too fast that you crash all day long. If you don't crash at all in a race, with a car that can do atleast 320kph, I guarantee you will atleast come in the top 3.