What is the strength of six sigma?

Six sigma targets variation reduction in the process. This is based on a robust methodology starting from strong problem definition process, detailed analysis section - which takes care of measurement system errors, indepth anlaysis of root causes and validating them, establishing solutions and deploying them with best in class tools and establishing controls so that, result can be sustained.

All these steps have proven, widely researched tools, which ensures you get an optimum result and can be sustained. This brings down the variation in the process.

No other tool provides such a definite methodology for variation reductions

Six Sigma gives target for defect reduction3.4 defects per million. Other improvement methodology don't give any target. It also start training people for different roles in six sigma. 

 

Reduce variation, maximize profit, cost saving, external and internal customers satisfaction, improved performance and reduce process cycle time.

If you are already an experienced quality professional, the only strength is marketing value. People respect labels and find it  easier to listen when you have one. If you are not a quality proferssional, you might get an expedited study in1/3 of what quaity professionals do, but a certified quality engineer will know more. A CQ Manager should be entrusted more, IMHO