if you mute might as well unfriend?

mute is more about muting posts so they don't come up in your new posts/update list so isn't really about the person. Necessarily. So, nope.

if parsival keeps muting this person, doesn't it makes more sense to unfriend instead?

Yes, but some people plurk oodles of things with many interesting & some not - so *shrugs*. I never use mute becuase of my damned curiosity.

Exactly Moggs, I couldn't decide because it wasn't all bad and she's hot. I just unfriended the person, hope no karmic boomerang

Amanda I finally unfriended this person after her last 10 consecutive posts were negative and/or just noise.

Wondrous it's a tuff decision for me; i always agonise over it.