Having known some students of both these colleges, I can say that both the colleges are really good in terms of infrastructure, culture, and faculties. There are of course some differences too and for that let me share with you a few details.

• K J Somaiya has better infrastructure and the campus is located at the heart of the city. SIMSREE doesn't have such a big infrastructure.
• SIMSREE has a better ROI than K J Somaiya. 
• Placement usually depends on your profile and how you perform in your management education & certainly performance in interviews.
• Professors, peers both are good in both colleges. 
• At SIMSREE, the finance course is much better as there are several guest lecturers visiting from JBIMS.
• Both SIMSREE and K J Somaiya’s program in MMS is Mumbai University affiliated. Its degree is acceptable for several government jobs as well.

It must be noted that PGDBM is not offered at SIMSREE rather the institute also offers MMS in affiliation with Mumbai University.

Also, while choosing between MMS at Sydenham and K J Somaiya, it is suggested that you talk to alumni of both colleges, which would definitely give you a clear idea.