Hi Disha!

IISER- Indian Institute of Science Education and Research is better than VIT Vellore as VIT is a private institute and IISER is a reputed government college.  IISER will be more beneficial if you want to pusue pure science and research.  If you plan to do masters then too the IISER tag will help you.  But if you wish to do engineering course sch as Btech in CSE or IT then you must join VIT Vellore as its placement records are incredible.

Hope I answered your query, thankyou!