If you are planning to migrate, do an international MBA. I did the USQ Australia MBA at CA Sri Lanka. Great course that provides latest knowledge and skills. But not sure whether it has OM specialization. Also heard that University of Wales MBA is great too.
If you are doing a local one, do it at PIM or Colombo University. Don’t ever do the Japura or Kelaniya MBAs. Especially the Japura teaches you outdated knowledge with arrogant and egoistic lecturers like Hemantha, Shyamen and Opatha.