The main difference between SSL Certificates is the level of "TRUST" the visitors perceive by visiting your Web site.
Consumer confidence is boosted if they can find information about your company identity, which has been authenticated by a recognized authority,(Verisign, Geotrust), the more information can be found, the greater will be their level of confidence.
So the main difference between SSL Certificates is the degree of investigation about your identity the certificate issuer will undertake. Depending on the level of authentication certificates are called Domain Validation, Organisation Validation or Extended Validation Certificates.
See our SSL for examples of each type.