hi,

the both of the institute you have mentioned is excellent for its academic curriculum, college infrastructure, faculty students ratio, research opportunity, excellent labs and exposure for international internship. there is many notable alumni you may have heard of, who has completed their bachelors from iit kanpur or  Indian institute of space   science and technology. however based on the students review I would prefer to IIST for aerospace engineering since it is well connected with ISRO, which gives the opportunity for students to real time practical experience while studying the bachelors courses.