Hey ChinoXL,
I personally don't believe that seeing a puppeteer affacts the quality of the character or performance. A good puppeteer can emote whether fully visable or not.
However if it is a technical question, like "Should we see puppeteers during a video/film shoot?", then I would say the performer should be unseen. Visually it is distracting to watch a good puppeteering performance on screen and then suddenly see an arm or a head pop up.
It all depends on the menaning of your question (as fivefingers has alluded to).