What's the difference between Pan, the mythical Greek god, and Hell, the mythical Norse/Pseudo-Christian underworld?
In this case the difference would be that the god Hell is much less known than Pan. But then again that is completely not the point. The point is, what is the difference between a pan flute and a hell flute. When saying something is a pan flute, the vast majority of people would imagine a flute made of tubes, i.e., the emphasis would be on flute. When speaking of a flute of hell, the vast majority of people would imagine a flute spewing flames, or being played by a devil. Which of those two images fits the setting of PS best?
Similarly, most people would think a claymore is a big sword being used in medieval (western) times. A Tai Chi sword brings up images of an oriental setting, or people doing slow movements in the park.
Of course there is a minority who thinks hell is a place known for it's soothing flute sounds, and that people meditating to this sound make very cool swords. But I would be surprised if even they would think a Tai Chi sword from Hell would fit PS as much as a pan flute.