Having to know some people studying at both Simsree and KJ Somaiya and here are some things that you should know. They both are equally good.

• Both the institutes, for their MMS course, teach the same syllabus specified by the University of Mumbai. So, according to the content, there is no difference.
• This is generally a good thing that you are specializing in something that roughly 4 to 5% of the batch will specialize in. 
• It is not as difficult for the placement committee to get companies with specific profiles.
• The institutes have been there for a fairly long time and both have a steady pool of recruiters. Therefore, placements are not very problematic. 
• Having said that, placements depend on multiple factors, and nothing can be guaranteed.
• K J Somaiya has more full-time faculty members whereas SIMSREE has more visiting faculty members. But cannot say the same about the operations specialization.

Irrespective of where you go, your responsibility is to get better, participate in competitions, do certifications, and improve yourself holistically. The institute cannot impose anything if you have no intention of doing it.