Percentages flatten context
A 60% label cannot say whether the hardest question has been answered. It often rewards optimistic reporting because a number is expected.
Hills show the work state
Uphill and downhill positions make the key distinction explicit: are we still solving the problem, or are we executing an understood plan?
Use both when needed
A delivery metric can still be useful for operational work. For shaped product scopes, use the hill chart to discuss certainty and blockers alongside the timeline.