Technically singlespeed is better since it is more advanced. It is also superior because you can conserve energy by coasting and it is better because it is safer over rough ground. But I honestly think that until i tried fixed for a few months i never properly rode a bike before. It taught me a lot about spinning and even sizing a bike correctly, but maybe im a slow learner and couldnt learn without riding fixed.

Traditional training calls for riding fixed the first part of every season to get your spin down and develop strength.