The voice Prism is superior in many ways, but in a live setting ... there is a MAJOR drawback to using it. When you change patches, the signal is muted for a second. Effects stop - voice stops ..... not a pretty sight for a quick change in the middle of a phrase. If you just leave an edit window open, and turn a particular voice on or off in real time ... it's fine, but a program change makes it hiccup.

Now, for the good stuff:

1)FAR superior effects and more of them
2)better control of voice formant (gender)
3)more real time parameters with dedicated knobs - effects, level, pan, whatever...
4)phantom power
5)mic mute button(great on breaks)
6)overal tone of voices is more realistic than the competition, but it's NOT earth shattering. A fine tuned ear will appreciate the difference.
7)GREAT screen - color, bolness ... easy to read. Really easy on the eyes in the dark.

In short ..... the TC is a much better piece.
Will it make you sound MUCH better in a live performance? Hard to tell - the subtleties may not come across as dominant in all cases.

My advice is to ALWAYS keep the lead vocal just ABOVE the harmonies(volume setting)so the realism is not lost. All harmonizers are a little fake sounding by them selves .... the trick is .... never let them work, BY THEMSELVES ! Keep them tightly woven around your lead vocal and sing believable phrases that make sense in a harmony arrangement. Don't just expect to hit the button and sound like the Beach Boys .... ain't ginna happen, my friend. Vocal arranging is an art in itself. In my world - it's the MOST important part of any performance.