Many web browsers now will differentiate the "padlock" placed beside a web address when the website uses different types of SSL/TLS certificates. These certificates are used to generate a secure session in which data is encrypted between your browser and the destination web server.
The example you have provided is a difference between eV (extended Validation) and "regular" certificates.
In the case of eV certificates, there is a much more rigorous, and in depth procedure when obtaining such a certificate. Company information and owner information are examples of details required in a eV certificate. It allows visitors to identify the website, and verify the company who holds the certificate, is in fact the one running the website. Owner information and such are not required when requesting a "normal" SSL/TLS certificate.
Firefox makes a bigger differentiation for eV certificates, where a simple green padlock is replaced with a wider green bar containing the company's name and country abbreviation (US/CAN/UK).