|Long, unpruned braches curve gracefully downward|
I drive by so many houses where the forsythia have been pruned severely into unnatural shapes like globes and squares. Extreme pruning or pruning too late eliminates most of the beautiful yellow spring blooms. So during bloom time, you will see these clipped shrubs with only tufts of yellow on the top or on the sides where pruning didn't cut as deeply into old growth. These sparse clusters of blooms remind of a child who tried to cut his own hair.
I say, "let it all hang out". Put your forsythias in beds and borders where they can take on a more natural shape. Save your topiary skills for your evergreens.