I have always used the Helicon harmonisers, from the PA1 and PA2x, but just recently I had the chance to try the new Digitech VL3D.
I have got to say the VL3D, was nowhere near as clean and authentic sounding as the Harmony M Pedal.
The ONE thing I liked was the easy access to controls like a compressor, and other ambience controls fro just the original vocal. But the harmony voices were very average in my view.
I think if you stick with any of the TC Helicon products you will not be disappointed.
Dennis