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It is possible to easily remove / add users, or edit bucket / task details, therefore any error is easily correctable. In addition, since there are lots of intermediate steps when adding information (navigating to new pages and clicking 'ok'), errors will likely be more rare in this design.
Overall:
Overall, this This design is easy to use and individual pages are very simple, but the overall it is more complicated than the other two designs. Having multiple pages to navigate through makes the layout of the individual pages less complex, but the website as a whole becomes more complicated to navigate through / learn, and there are more sub-steps to complete for each action the user takes.