If you are a true science lover, then IISERs are the best option for you. Although institutes like IISc, NISER, CEBS, IACS, and a few IITs, also offer similar science-oriented degrees IISERs resources, exposure, and research culture are second to none.
IISERs offer a 5 year integrated BS-MS degree which helps avoid the hassle of applying for a Bachelor’s and a Master’s separately.
So, if you are a research enthusiast and want to pursue a long-term educational program to fuel your passion, then IISERs will serve you best. However, CUSAT can be considered if you are looking for a course or opportunity that is unique to CUSAT only.