Top Speed
The vehicle with the top speed is the Chevrolet Camaro SS at 260 km/h (the Subaru WRX STI GRC and Dodge Challenger SRT8 are faster at 290 and 285 but they're not yet available). Rally cars are also fast and have the added advantage of also having better handling than the mucsle cars.
Acceleration
The Ariel Nomad has the quickest acceleration with 3.60 seconds. Althoguh buggies in general have quick acceleration because of their light frame they are also susceptible to being squashed under the tyres of the larger monster trucks.
Handling
The vehicle with the best handling is the Ariel Nomad which has a handling rating of 2.10 Gs. Buggies in general are the best for stunts because of their light frame and are also great for drifting around bends without losing your footing.
Best All Round Car
The Range Rover Evoque is the best all round vehicle. Although it doesn't have any particular advantages it doesn't suffer from any significant drawbacks either. SUVs in general are great at performing long nitro boosts.
Nitro Button
If you tap the nitro button it consumes one chunk, while hitting it multiple times makes the nitro stronger.
Quicker NItro Recharge
If you drift for long enough you will be able to speed up how fast the nitro recharges.
More Nitro
You can earn more nitro by destroying any junk that is in your way. Doing this is the easiest way of gaining a recharge.