Vilas: I disagree with your premise that flaps full landings are more difficult. In any aircraft you should be trimmed for the configuration you are in. On the Airbus that function is done for you by the auto trim system. No extra effort is needed to move the controls, be it stick or yoke.
Flaps three is used for abnormals due more to less drag for single engine go arounds and second segment climb gradient requirements. In Direct Law it is necessary to manually trim. Flaps three allows for less trimming and a better chance at a stabilized approach.
Flaps full provides greater tail strike protection clearance on the 319 and 320 and only .5 degree less than config 3. I use flaps full on the 321. I want the extra drag and lower speeds on touchdown. The difference is 21 degrees flap angle versus 25 degrees. I'll use that extra few degrees.