Which unit of measurement should be used for a project team that wants to optimize changing priorities?

Hours tie estimates to time, making re-planning expensive and difficult when priorities shift, as all time-based commitments must be recalculated.

Features are a unit of scope, not a unit of effort estimation, and do not help the team quantify or compare work items to optimize prioritization.

Packages are not a standard agile estimation unit and do not support the kind of flexible, comparative sizing that changing priorities require.

Story points measure the relative size and complexity of work items without tying estimates to a fixed schedule, which makes them ideal when priorities change frequently. Because points are not anchored to specific dates or durations, the team can re-prioritize the backlog, add or remove items, and re-plan sprints without invalidating all prior estimates, enabling flexible, value-driven delivery.