My brother has studied at IMI Bhubaneswar and it's the best because of its brand value. It is a new and upcoming institute with IMI Delhi’s reputation and brand value.
The following points explain a brief overview of the institutes:
Now, the difference to be highlighted in the degree is that FMS BHU will give you an MBA degree whereas, IMI will give you a PGDM degree; although this is not a huge difference you might choose an MBA over a PGDM program.
So, finally, the choice lies with you because both institutes are quite similar in academics, facilities, and opportunities. It will definitely not create a huge impact if you choose one over the other.