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.