That depends on your budget and needs. Dealerships have reliable, high quality workshops that can provide specialized service to car brands matching those they sell, as well as general service for all cars. They are likely to have the best supply of parts for a dealer-related brand. However they are also one of the more expensive options. Independent garages and mechanics are often cheaper, but it is important to choose wisely, as reputability can vary. And specialty garages are a great option if you need specialized knowledge or know there is just one, simple task to be performed (e.g. replacing brake pads).