I assume you are specifically talking about the CSE branch only. In that case, IIIT Hyderabad is certainly better than ISM Dhanbad in many ways. It has better research opportunities, curriculum, placement scenarios, better recognition among software companies, and a higher number of people qualifying for ICPC and GSOC.
However, everything about IIIT Hyderabad is CS-tailored so if you are open to other options or aren’t yet certain of CSE, then choosing ISM Dhanbad will do you more good.
So ultimately the ‘better’ college depends on your choice.