I am convinced that any of the keyboard harmonizers can do a decent job.. It is usually human error that gives poor results.

I would say 9 out of 10 folks are not setting the thing up right..
Folks use the wrong settings, wrong balance, wrong mic, wrong cable (impedance)

… and mostly wrong time to use it
Here is a quick demo to show the G70 harmonizer, most folks have never heard a G70
The first part on the recording is straight up … the second part starting at 2:25 is pitch correction (I used my best Chas imitation on this part

).
https://app.box.com/s/yme218c69917df1b8l0yora9v4sfikqn