The verdict
If your team already runs on Notion and wants agents and meeting notes next to the real project data, pick Notion AI. The value is context, and it is part of the Business plan, so count every seat before you decide.
If you want a fast task list that works without setting up a workspace, pick Todoist.
If you are not on Notion, Notion AI is the wrong purchase, because you would be buying a workspace upgrade for one feature. If you are on Notion, you may not need Todoist at all. I stuck with Notion for task management myself, partly because of its flexibility. For a team with no workspace yet, I'd start with Todoist.