Where Todoist fits best
Task-management maturity, filters, labels, collaboration, quick capture, and cross-platform task workflows. Todoist also has real calendar planning: day and week layouts, time blocking, drag-and-drop scheduling, and synced Google or Outlook events.
Ramble turns natural speech into structured tasks — projects, dates, deadlines, priorities. It is capture, not a secretary.
Where Rio fits best
Choose Rio if you specifically want conversation with a secretary across more than tasks — calendar, habits, and knowledge in the same account. Not because Todoist lacks calendar planning.
Where they overlap
Both capture work. Both can put tasks next to calendar time. The difference is depth versus breadth: Todoist is a mature task system that also plans a day. Rio is a personal assistant that happens to include tasks.
Who should choose which
Stay with Todoist if the job is managing tasks well. Choose Rio if the job is talking to one secretary about the rest of a personal day.
Also see task management and daily planner.