Can I just say that at least two of the plastics are for different approaches to the Buzzz. Pro D is my favorite for a disc that I'm going to be breaking into an under stable mid, same with Elite X. I'm not hoping that it holds forever- if anything, I want it to break in faster so that I have something to cover my under stable shots.
Also, I like Z fine, but often I play in a bit colder weather, and can't get a grip on that to save my life. I actually prefer ESP plastic, ESPECIALLY the super colors. Only it takes a while to break them in to get that really great grip on them. Z are probably my lest favorite plastic of the two (ESP/Z) because I just can't seem to get a decent grip on them. As for FLX- I think it's crap outside of the Drone or Challenger.
If you're worried about flipping or having them peter out, maybe try a heavier Buzz. I've been throwing a 177 ESP buzz for a full season now, and honestly it's the same buzz that I had gotten it as- a wind-fighting Buzzz. If your weights are low, you probably will see them start to get a bit of high speed turn earlier on. I'd compare your weights of the two and see what that does for you.
Also, it depends on the top of the flight plate- I've had some Buzzzes that are super domey, and others that are crazy flat. This affects the flight even more so- as far as I know domey are more overstable than flat ones.