Indian Institute of Information Technology (IIIT) are mainly for IT field. 

One can apply for IIIT with Jee mains score. 

Next,  for which is better as I mentioned that IIITS are for information technology sector some branches of a few IIITs are much better than NITS.  For example, I we talk about Computer Science from IIIT Hyderabad, then it's one of the best in Nation. 

Else, generally NITs are preferred more than IIITS. 

Hope this will help. 

Thanks.