That is a complex question. In my opinion there is no single answer. You have to find out what your particular skills are and then apply the appropriate form. A lot of the mainstream and modern martial arts are competition based. (Good on a mat, not in the street) Being involved in an actual street fight takes more than just knowledge.
In a case where you are much smaller than your opponent you may have to maim disable or even kill him. Focus on Combat art forms. DO NOT think that you?re going to take Karate or Kung fu for 3 months or a year and dominate. I have seen more people earn a quick trip to the hospital that way.
The best answer is always to learn how to not fight. Any good traditional art form will teach you that.
