There are many car rental options on Madeira, and honestly the whole industry has become so streamlined that prices generally are on par whether you pick Europcar, Sixt or Madeira Rent. We recommend the latter, since it's a local company that we have used everytime we rented a car before moving to Madeira. They have better overall ratings and because it's less of a corporate business such as Sixt, Europcar etc, the ceiling is higher, so to say. Madeira Rent used to have much better deals than everyone else, but the rise in tourism has unfortunately caught up, so renting a Mini Cooper Cabrio in high season will set you back a lot of money, which simply isn't worth it, but it of course all depends on your wallet. 

Madeira Rent has an agency in both the airport and in Funchal, which is handy if you only need a car for a few days of your trip. That way you don't have to go to the airport. 

The number one advice from us, you should follow is to never rent the smallest (and usually cheapest) car you can get. Madeira is a mountaneous island so there will be a lot of driving up and down. We once borrowed a Fiat 500 and it could barely drive up some of the steep hills - no joke. 
