Each make and model carries it own rating for insurance. In some cases four door cars are less expensive to insure than 2 door cars. If you are comparing the same year, make and model than this could be true. If you are comparing different makes and models than it might not be the case. Other factors such as engine size, safety features and cost to repair are factors.

You can see how different makes and models effect the rates by getting a free insurance quote here.