Hi again,
Well, generally Masters in Management degrees are not my strongest area of expertise, fyi. You may have better chances, as they are often slightly less competitive and take younger candidates. There are some variants of 'Masters of Operations Management' or 'Masters of Operations Research' at least at US schools, fyi, if you truly stuck with that career path. I would say very broadly that the MBA may open MORE doors and is more general and a little more 'standard' in terms of curriculum and expectations of what MBA graduates are capable of, especially at well-known schools... the Masters in Management can be considered to be a bit more 'vague' and it also depends on what companies you are targeting post-MBA, and where they go to hire and recruit! If you know you're interested solely in a particular area (finance, marketing, even operations), sometimes a masters in that area can still serve you well, if any uncertainty, an MBA generally lets you explore and learn about a wider variety of areas. Best advice generally though is to speak with hiring professionals and those who work at companies you're interested in working at, do some informational interviews etc, and find out how they view different degrees.