Should I opt for ITM Navi Mumbai or Amity Business School?

It's difficult to compare ITM Navi Mumbai with Amity Business Schools as both the institutes are on a similar level so you can choose one over the other based on your personal preferences. The batch size is quite similar. Amity is a good choice for North Indians while IMT is great for South Indians. 

If I had to make a personal comment, I would say that Amity is slightly better considering its location, quality of education, and the exposure offered. It also enjoys a better brand name than IMT. Amity Business Schools was the first to invite Marketing specialist Philip Kotler. 

Both the institutes take in candidates with good profiles and communication skills so make sure you have worked on them. The ROI might be less for average students so it all eventually depends on your hard work.