I have found that it is much easier to make calls using headsets. This is so for cell phones and computers. In the case of computers, relying on the microphone and desktop speakers alone does not always give the best results. The microphone generally picks up any ambient noises that are easily entwined in the audio being sent to the person on the other end of the line. There is also some level of sound loss when you have to listen through the speakers. Using a headset eliminates 98% of those problems.
When you have the speakers right up to your ears, there is no loss of audio, or very little, since there is no space for external noises to interrupt through. The microphone would also be closer to your mouth, making your words more understandable. Many professionals use headsets as they enhance the quality of their work. Making calls from your computer using a headset is a smart way of communicating effectively with the person on the other end of the line. You do not have to spend a lot of money to get quality headsets. Get one that is within your budgetary range.