I'm with UD on this one. I have the voice prism plus and have tried the digtech as well as yamaha and Ketron keyboards with them built in.

Well there is definately a difference in quality. I think that is because you have 24bit sampling as against 16bit sampling.
The results are, of course, very subjective.

But that's not the only difference. As UD stated, there are many more parameters to adjust and quite frankly when I first got the box I was overwhelmed by it all. It would have been much easier to get the Digitech EX with the sliders but I had paid my money and decided to get familiar with it. I had bought it as a second user deal for about $700 and was pretty sure I could get my money back anyway.

Am I glad I didn't. It takes practice to get anything more than simple (third above) harmony to sound realistic but when you have mastered it the results can be very realistic (IMHO)

I was probably guilty of looking for the "magic box" initially that is mentioned above but now that I have taken the trouble to find which of the 3 major or minor scaler modes are suitable for the song in question (or even building a specific custom scale) I am satisfied with the result.

The more robotic sounds are the ones that just take the control data from the chords played over midi. Whilst this is suitable for a few songs the scalar route is far more authentic when the right parameters are set up. There are patches that are supposed to sound robotic and weird such as the alien, drunken sheep and telephonic ones but these are just places to store your own settings as far as I am concerned.

If that means "twiddling" to some people then that is the price you pay as it is a voice crystal and not a crystal ball.

In addition to the harmony features, I also use the reverb/delay/compression/gate facilities and, as I have the plus this gives me more realist gender changes for both harmony and doubled voices.

I am thankfull to this forum for bringing the TC box to my attention in the first place otherwise I would have had got what I consider to be an inferior unit and, believe me, I need all the help I can get on my vocals.

Regards - Keith