For a Perfect Manhattan, how is the vermouth balanced?

In a Perfect Manhattan, the balance of vermouth is achieved by using equal parts of dry and sweet vermouth. This combination creates a unique flavor profile that complements the whiskey without overwhelming it. The sweet vermouth adds a subtle sweetness and richness, while the dry vermouth contributes a crisp and herbal note. This harmony of flavors is what makes the Perfect Manhattan distinct, providing a balanced and nuanced cocktail experience for the drinker.

Using only sweet or all dry vermouth would skew the flavor in one direction, resulting in a cocktail that either lacks complexity or does not showcase the full range of flavors found in a well-made Manhattan. Topping the drink with extra whiskey would also not maintain the delicate balance intended for this cocktail.