In Japanese history, a ninja (忍者) is a warrior specially trained in a variety of unorthodox arts of war. These include assassination, illusion, espionage, and various martial arts.
Samurai warriors described themselves as followers of "The Way of the Warrior" or Bushido. Bushidō is defined by the Japanese dictionary Shogakukan Kokugo Daijiten as "a unique philosophy (ronri) that spread through the warrior class from the Muromachi (chusei) period. From the earliest times, the Samurai felt that the path of the warrior was one of honor, emphasizing duty to one's master, and loyalty unto death
A Ninja would do anything to avoid a one on one battle instead they would choose to assasinate their victim long before it ever go to a physical confrontation. So I pick Ninja via Ninja Star to the back of the head while Samurai is sleeping.