Out of two it is better to go for IMT Nagpur. Atleast you get the brand name IMT moreover the placements at IMT Nagpur are way better than ISBM Pune. Also, I would rather suggest you to go for IMT Nagpur only if it is mandatory for you to pursue your PGDM this year itself. But in case you are in a position to take a drop and prepare simultaneously while doing some internship simultaneously, it would be a better choice. Although IMT Nagpur is preferable over ISBM Pune, but it would be a wise option to take a drop and try next year rather than joining these colleges.