It's not about degrees or even jobs, it's about education. There will always be someone better out of the 10 or so resumes sent for a job. How do you stand, what do you have?
If you want to be competitive, MBA offers an edge. It's all about survival of the most able, in this case, with a post graduate degree (since there is a requirement of a 2-year managerial experience requirement at most valid universities) you give yourself an edge.