Final answer:
Both presidential and vice-presidential debates are valuable to voters as they provide insights into the candidates' policies, their ability to handle stress, and articulate their visions clearly.
Step-by-step explanation:
When considering which debates are more valuable to voters, option C, Both presidential and vice-presidential debates, is generally seen as the most valuable. Presidential debates provide a platform for the main candidates to present their visions and policies directly to the electorate. Vice-presidential debates, while often seen as less pivotal, still offer valuable insights into the policies and the quality of the candidates who are a heartbeat away from the presidency. Moreover, both types of debates serve as an important check on the candidates' abilities to perform under pressure and articulate their stance clearly.