I hear what you're saying. I found the newer airbuses are much better but the older fins (I have flown a handful that are double midget serial numbers) do hunt around for the speed. Say you're climbing out at 250 kts and the plane is doing 3000 fpm. Pulling VS and dialling it back to 2000-2500 fpm is usually pretty smooth when you start pulling it back further to 1000 fpm the speed tends to increase, then the plane pulls a bit too much power off and the adds it again. Same thing at ALT * sometimes the plane pulls off a bit too much power and hunts around for a second. It can also be fairly aggressive pulling speed off. In open climb the climb rate will decrease to maintain the 250kts (or what ever target is) if you slowly decrease the trust manually it can be much smoother.