What are the advantages of Interrogatories over depositions? What are the disadvantages? When would you use one over the other?

Suppose that you have been handed a case involving a typical automobile accident. Defendant B rear-ended Plaintiff A at a red light. What could be 20 interrogatory questions that the plaintiff should serve on the defendant? Making sure that they abide by your state's limitations on interrogatories and that they do not request privileged information.