Final answer:
Product differentiation is the most important characteristic in determining a customer's choice of service.
Step-by-step explanation:
The characteristic that is the most important in determining a customer's choice of service is product differentiation. Product differentiation refers to the unique aspects or features of a product or service that set it apart from its competitors. These differentiating factors can be tangible, such as price, quality, or design, or intangible, such as reputation, customer service, or brand image.