From a subjective perspective:
A319: light and nimble, like a Ford Fiesta
A320: more like a Lincoln Continental, sluggish, but in a nice way.
A321: we need additional line training to fly those!
Very noticeable as well is the difference in rotation logic on the 320CEO and NEO. Pilots new to the NEO always rotate much faster the first time they take off in a NEO. There is also a marked difference in handling when the flaps are in transit from 1 to 2.