Prague has a well developed public transport system that includes metro, buses and trams.
If purpose of your trip is to visit only Prague I wouldn’t recommend renting a car. Public transport is cheaper and besides you will avoid problems with parking and so on.
But if you are planning to visit other districts of the Czech Republic for a day or so it would be wise to rent a car.
As for me I thought a lot about this problem during our trip in Český Krumlov. If we had rented a car we would have managed to visit not only Krumlov but e.g. the Hluboká Castle situated in Hluboká nad Vltavou and considered to be one of the most beautiful castles in the Czech Republic or other places like Karlovy Vary, etc.
Nearly every village in the Czech Republic has its own castle. In most of the cities the centre is very interesting and if you have enough time it would be an exciting affair to rent a car and take a trip around the country.
Roads in the Czech Republic are quite good and simple.
This website will help you to rent a car in Prague and the Czech Republic.
It offers the widest selection of cars at the best prices.