There is no car in version 3 like the DC2 back in version 2. In short, there is no god car. All cars are equal. Some are just more equal than others.
Good battle cars are the 6 gears cars. Especially the NB8C, S15, SXE10 and GDB. But bring these four to wet conditions they will die.
The Hong Kong players have ranked the Capp as the best TA for dry and the R32 for wet.
Myogi is still dominated by the GT-R Skylines. One for each direction. The Capp is pretty good for Myogi as well.
The entire Silvia family is good on Usui. The GC8V seems to be the odd one out.
The fastest car on Akagi down is now the S14Q aka the Kenta Mobile. Uphill is the Evo3.
The AE86 is back to being the king of Akina down. The GC8V is preety good up as well.
Irohazaka is now the Evo playground, with the Evo4 owning both the up and downhill.
Akina Snow would be the Celica GT4.
The Hondas are good on Happohagara, with the exception of the S2000.
Shomaru: Capp and Altezza. The RWD ER34 is good here as well. Startup for battle plays a very big role here. Cars of choice are the GDB, Altezza and GT-R34.
And finally Tsuchizaka. This road is so smooth, it feels wet. The 4WDs do well here, the GDB not so much as the rest. Watch out of the oilspill and beware of the last section of Inbound. It's like Happo's snake bends but a lot worse.