I've been using the vest forever - I won't say its my best friend, but I do find it very helpful, and wouldn't get rid of it.
Sometimes it doesn't seem like it does a whole lot when my health is doing well, but when I'm congested, it does wonders. Its important to remember that you have to work the settings to get the different vibrations (or shakes) to reach the different areas of your lung - one setting won't get your whole lung. It's also important to remember that you still need to huff. The machine loosens it up, but its up to you to cough it out!
I recently got the acapella for use at work and traveling, but I don't get it. I have tried all the resistance settings, it doesn't provide a challenge to me at all to breath with it. I just feel a very slight sensation. Does anyone know if there is a special trick to it? Or maybe my lungs are too clear for it to work as well as it is for others?
Anyway, back to topic. I prefer the vest because I can do it anytime by myself. Living on my own, that is a huge benefit. It also takes up a lot less room than a BD table (I HATED having to put that thing up and down twice a day!!!) Mine was covered by insurance, so cost wasn't an issue for me - although I am not able to upgrade to the newest model yet (which is fine, I'm happy with what I have).