The primary benefit of an effective sales and operations planning (S&OP) process is that it enables a direct and consistent dialogue between operations and senior management. This dialogue helps ensure alignment and coordination across different functions of the organization, leading to better decision-making and resource allocation. The other options describe specific aspects or outcomes related to planning and prioritization, but they do not encapsulate the overarching benefit of the S&OP process, which is improved communication and integration within the company's leadership and operational teams.