I do not have a six sigma belt certificate but I have heard about it from employees and friends. A friend of mine was able to get a job as a Lean Manufacturing Engineer because they received a six sigma green belt. With the knowledge gained from taking a six sigma course my friend is able to decrease the time and increase production output on the production floor by knowing how to organize each section of the division. With this certificate you open the doors to becoming a project engineer, data scientist and etc. Benefits of having an employee that knows six sigma can help improve customer satisfaction, customer loyalty, employee satisfaction and can help gain better partnerships. A six sigma green belt certificate differentiates you from any other candidate because you learn ways to make good business decisions by using analytical skills.
If six sigma is not implemented within the business strategy or objectives then the likelihood of failure is high. If executives are not engaged in the process then the employees will not be and therefore the values learned from a six sigma certificate are useless.

References:

Finding a Six Sigma Green Belt Certification Career

http://www.sixsigmadaily.com/what-are-the-benefits-of-six-sigma-certification/