Who has the cheapest car insurance?

Technically, there is no answer to this question. No single company will always have the lowest price on car insurance. That's why everyone says you can save money by switching to their company.

All insurance companies want to attract certain customers and discourage certain other customers, and part of the way they do that is price. If the insurance company does not want to insure people that are classified in the same group as you (on many characteristics, possibly including age, gender, location, etc.), they will either outright decline to give you a policy or will give you a high price.

If you want to find the lowest price, you have to get prices from as many companies as possible. A good place to start is an independent insurance website, where you can compare car insurance quotes from good insurance companies.