Oh boy 😂! I had done some good research about this before joining IITK for AE (I had spoken to quite a few people about it)
So, in terms of placement, IITB is the best. But this includes placement of AE students into non core jobs as well.
In terms of research and academics IITKanpur is the best. They have some of the best professors, publish some of the best research papers, etc… .
In terms of facilities like labs, models, etc… . IITKanpur is way ahead of other iits. It has its own wind tunnel, actual aeroplanes, an airstrip, along with the best labs.
Now let me lay out one more criteria. How interested are you? Aerospace in a very deep field, in the sense most acclaimed core companies do not even hire ug students as they simply don’t have the knowledge. So if you’re really into working in the field and want to pursue higher education then go for IITKanpur but if you’re not really into getting a core job then it really doesn’t matter which iit you go to all are the same.