I think BHU is a grad level course while JNU offers only at Masters and Doctoral level courses (MSc, M.Phil and PhD in Environmental Sciences), so technically you can go for BOTH.

But given the choice JNU Environmental Sc has no match. This is because of

1. Extensive exposure
2. Established research groups and properly oriented labs
3. In terms of financial expenditures
4. Campus life etc

ALL THE BEST