From experience I would say the heavier boats are less flighty, more forgiving and easier to drive.
But Hell... what do I know?
Humm, from experience I say light boats are more fun to sail.
I find F18 sailing (outside of fleet racing) a little dull by comparison and I know that I'm not the only one.
Besides I know the heavier FX-one (150 kg) was significantly less fun to sail then my lightweight F16 because it was significantly more flighty, less forgiving and harder to drive. I put that down to its use of a cut-down Tiger F18 mast (far too stiff), use of F18 daggers (far too long and too much surface area) and hull volume too much centralized under the main beam for 1-up sailing (stern dragging or pitchpoling). As a singlehander it should have been designed noticeably different. As a versatile boat (1-up + 2-up) it should have been designed alot more clever, especially in the keel line. Overall boat weight was hardly a redeeming factor in the way this boat sails.
Therefore I don't think there is much truth to the rule of thumb you state.