ESS and Technology at IIT Kharagpur is focused on the natural resources and resource management technology which is used at various operational level. Whereas, Maintenance and Tribology at IIT Dhanbad is more focused on the resource allocation of regional tribes and management of endemic tribes. So, it completely depends on your interest. Consider what interests you and suits you. However, IIT Kharagpur is slightly better in placements than IIT Dhanbad.