The results are the same, but the working method is quite different. I wanted an additive Blue/Green like the Zone VI head for a long time and even tried to make something. Eventually I came up with a working method for color heads that suits me well; I've thought about trying to write that method up for some time.
I'm curious what system people use for color heads that works as well as the Blue/Green additive. I like to have the ability to adjust the highlight or shadow somewhat without new test prints (or exposure charts). I believe the additive heads accomplish that, but never did get a chance to work with one.