My daughter has the Hill-Rom 104. She likes it, and likes to have the option of using either her half vest or the full vest depending on how she is feeling.
When my son needed a vest I decided to go for the Respirtech vest. Although I am not the one with CF, I like the RespirTech vest better, because it seems to just have a better feel to it - hoses clamp on, they are larger and seem better build and made from a heavier material. I also like the shape of it better than the Hill-Rom 104. I also like the material the vest is made out of better than the Hill-Rom vest. The only down side with the RespirTech is the beeping! It beeps at the end of every cycle, which I cannot remember if it is every 5 or 10 minutes, but whatever it is, it's too much

They say they are working on a change for that for the next model, but probably cannot change it for the current one.
Sakasuka has a lot of good info about the RespirTech machine and the difference in the technology, between it and other machine.... something about the wave type.