I used the external Digitech Harmonizers for years. The latest one I had was the Vocalist II rackmount model. The PSR harmonizer is better than it was and has more useable preset options. I'm sure the newer Digitechs are much improved, just as I'm sure the next generation of keyboards will be better and so on and so on . . . ain't it fun????
I do have a question about the PSR2000 vocal harmonizer though, but I'll start a new string for it.
DonM