My take is that the Soul Preacher is a simpler VCA compressor, the White Finger is a FET optical, and the Black Finger is tube. The optical will have a slower attack by nature. I have a feeling they Soul Preacher and White Finger can sound similar, of course depending on the settings. The White Finger should have many more settings that are useful. To me, the Soul Preacher has just a couple of settings, although they do sound great. The White Finger has a lot of settings that sound cool, depending on what you want. I have never owned a Black Finger, so I bow out on that call.