That quite depends up-to your interest to be very honest. One with the MNS degree has to serve the military soldiers that is the INDIAN ARMY so that's a very Special feeling right to serve them if you have genuine keen interest. You would be doing a BSC in the field of nursing which is a bit different than being called as a doctor after completing your MBBS. You'll be called as a Nursing officer after completing your graduation in MNS field. By doing MBBS, you can treat the people of this society anyone. So by both the ways you're doing some good for the society. So upon your interest choose the one that you will be happy to do the most.

Refer the sites below for more information..

https://medicine.careers360.com/exams/indian-army-bsc-nursing

https://www.careers360.com/mbbs-companion

Best wishes. Thank you.