This game I'd say is the best Need For Speed game yet!
Teir 1: Tuner: RX 8
Exotic: Alfa Brueno
Muscle: Camaro
Teir 2:
Tuner: Mitsubishi Elcipse
Exotic: Lotus Elise
Muscle: Ford Mustang GT
Teir 3: Tuner: Nissan 350Z
Exotic: McLaren SLR
Muscle: Chevrolet Corvette Z06
And also some hints for Canyons incase you have a hard time, Muscle cars are pretty good on canyons because they get going really quickly, faster than most other cars. Don't be afraid to break on sharp turns, and try to pass the opponent as soon as possible. Once you're in front, don't let them pass you at all. (Keep an eye on the rear view mirror once your in front to make sure they stay behind you). One of the secrets to Drifting is speed, if you can control the car while going fast and don't hit any walls, you'll get loads of points. Don't turn too sharp though if you are going really fast. You'll propell forward and hit the inside wall. Corvettes are good for Drifts.
For Circuits/Sprints I normally use Drafters because they are extremely fast and they will hit anything in front of you and still keep going the same speed.
Scouts are useful if you aren't good at finding shortcuts. But they aren't all that fast. And last, Blockers. Blockers are Neville and Samson. Samson is probably the better of the two. He uses Muscle cars throughout the game. But Neville will use the type of car that you do. You choose Muscle, so does he, you choose exotic, so does he, etc.
This game was great, and I'd say you should get it, but if you aren't sure, try renting it.