I have answered similar question to this. The best martial arts comes from your preference, whether it be hard first style like karate and muay thai, or gentle fist style like tai chi or jujutsu. If you cannot decide, try researching each martial arts that interest you and possibly take trial lessons from nearby martial arts school. In truth, there is no such thing as the BEST martial arts. Every martial arts are equally as strong as another, and can be used in any way you like, whether it be for fighting or for self-defence.