The yin algorithm (which is the basis for both plug-ins) has been developed to find the fundamental Frequency of a voice. There are a lot of other algorithms as well and each claims to find the fundamental most accurately.
But they have all one thing in common: they are only suited for a certain context e.g. polyphony or plucked strings.
The first formant of a voice will determine its pitch and its frequency can even rise above the other formants. That’s why pitch shifting sounds so strange - all formants are getting a higher frequency which isn’t natural.
I think that the results should be quite good, independent of the harmonical upper structure.
I can’t test it thoroughly - my voice is far too bad for that…
Here’s the link to Steve’s plug-in: