Mark for Action, or Use a Task?

Understand the differences between Mark for Action and creating Tasks and the best ways to use these features.
Mark for Action is part of the Marking feature and allows you to assign content items to yourself for action, or invite others to review them and take ownership. Typically, you'll use Mark for Action in an informal, on-the-fly manner when you're discussing something.
Tasks are a formal way to assign and track tasks for yourself or others (Pencil icon > Task or Actions > Tasks > Create a task). You can assign the task a deadline and associate it with a project, such as "Sales Kickoff January 2015", or save it as a personal task for yourself. Any Tasks that are associated with a project are displayed on the Tasks tab of the Project's home page.