Most of my friends have suggested that you should not take a gap of one year just because you want to prepare for CMI. This exam is difficult and they select only a few candidates, unlike JEE. It would be a waste if you lose the CMI exam with few marks or get rejected in the interview round. It would be better for you to join IMA Bhubaneswar. You can prepare for ISI/CMI examinations along with your UG studies.

Although IMA Bhubaneswar is also not a very good option because of the following reasons:

1. Academics: The academics of this college are ok. You cannot compare that with CMI faculties. They will complete your course and syllabus but you cannot expect anything new from them. There is also no wifi on the campus.
2. Hostel and social life: The hostel life of the college is also not very good. The food is not of good quality. You will also find that 4-5 people are accommodated in one room which makes it difficult to live. You will also find it difficult to study as there is a lot of mess.

If you don’t get better colleges like St. Xavier’s Kolkata and Jabalpur then you can join IMA. But if you join here you should start preparing for masters from another college. For this, you need to prepare for entrance examinations. 

IMA does not offer something special but it is better than central and state universities. Whatever colleges you will attend make sure that you clear your concepts in those three years. Although CMI is a very good institution you can also try for TIFR, IMSc etc. However, the course structure of IMA is good and you will also get the chance to enter good companies for internships.