C Star
The handling quality of FBW only depends on how the engineers tuned the computers for particular type of airplane. I do not consider the differences what you felt is related to inertia, I have flown both types and I do not remember any difference. The reason may be the calibration problem of FFS which you have flown.
And
The function of "F" in Take off, is marking the Vls speed of Con 1+F. That means, regardless Conf 2 or 3 which you have used for take off, when you have retracted the flaps/slats direct to Conf 1+F at "F" speed, even there is no acceleration, the the current speed will not be less than Vls of new selected configuration (= C 1+F), which is fail safe.
However, the function of "F" in Approach is completely different: They represent maneuvering speed of selected configuration (Conf 2 or 3). That maneuvering speed is (L/D) max of selected configuration and approximately equals to 1.4x Vs1g. Since for Conf 2 and Conf 3 for approach there is different Vs1g, so that means there will be different F for each configuration. Airbus formulated or approximated or related it to QRH "F" speed (which is good for take off) as 4 or 14% increase.