There is nothing more personal than having a face-to-face conversation. Exchanging e-mails is impersonal, speaking on the phone is a step up, but having a face-to-face conversation allows you to see people’s reactions and non-verbal communication.
Anyone that has had to interview someone for a job knows that body language indicates a lot about a prospective candidate’s persona. The same came be said when it comes to sales. Does your potential customer have his arms cross? Are they paying attention to what you’re saying? Are they smiling every time you mention their name?