Samurai Vs Ninja - Who would win?

On a one to one fight the Samurai is the better trained and more psychologically capable.

So the Ninja must rely on dirty fighting to defeat any well-trained samurai (and don't forget the samurai were not beneath using dirty tricks themselves!).

The Samurai considered the ninja (Shinobi) as so much vermin.

It depends on the circumstances. Ninjas were stealthy assassins who would easily overtake a samurai alone, the samurais heavy armor would not allow him the reaction time he would need if he were caught by surprise. . But in an open battlefield with enemies exposed, the ninja wouldn't stand a chance. Samurai were trained for open combat and were battle strategists. One-on-one, i think it would depend on the skill of the individual ninja and samurai.

The Ninja, cause Ninjas are cowards without honor who kill you by sleeping or because they use tricks to win!

The Samuray would be win in a fair fight I think.

Ninja as the Samurai would not see it coming.