Hands down, the mort important things on ANY car are your tires and brakes. If you have a Ferrari with bad brakes and worn out tires it doesn't matter how fast or how great the car is, you can't hold it on the road or stop it!
Your car can have 2 horsepower, or 2000 - if you can't stop it it means nothing.... Same for your tires, given that you only have a area of a handprint touching the road at any given time - if they are miss matched, worn, or improperly inflated you can't keep the car on the road!!