Between Sastra University and IIIT Sri City Sastra University is definitely the better choice. It has an amazing curriculum, placement records, and research facilities. The brand name is a plus point too. IIIT Sri City, being a new institute, has a huge task ahead to level up and compete with other institutions. Their facilities and the faculty are not up to the mark of Sastra University. 

The branch which you are interested in also plays a major role in selecting what is best for you. If you are inclined towards Biological Sciences, Sastra is perfect for you. Their Biotechnology, Bioinformatics, and Medical Nanotechnology branches are top-notch and they even have higher placement opportunities in CS and mechanical branches.

Quick stats 2021:

Sastra University is pretty strict when compared with IIIT Sri City. But you will have more learning opportunities at Sastra.