Whether a house's form is low slung, upright, clean lined or ornate, it should convey a definitive design intent. A good architect thinks of a house's overall shape as a sculpture to strive for good form.

Unfortunately, most new homes today misuse the "form follows function" dictum as an excuse for bad form. Too often, the designer comes up with a floor plan and a front facade the owners approve, then shrink-wraps the rest of the house w/ after-thought or canned exterior details. That's why McMansions tend to have the form of an amorphous mound with a perky front, to convey the design intent that says these houses are architecturally shallow.  

Proportion is the beauty that comes from the relative sizes of the architectural elements (windows, doors, roof, etc.). Like people's faces, where pretty ones have their facial features well-proportioned, go well together. Change the size of a feature like a nose to mess up the good proportion, the face quickly loses its appeal. 

Bad proportion is epidemic in today's new constructions. Their designs stop at having incorporated their architectural check list, don't go further to address how well the components go together, especially their proportions. 

Good form and proportion are more evident in older, prewar homes. Back then, the population was much less transient, owners think of the houses they build as life-long residences, or even as heirlooms, and thus spent more thought and effort on planning and designing.  

We should do similarly, especially since refining form and proportion can be done without increasing the construction budget. Just more thought and effort.