Both are good IIT’s but IIT BHU being an old institute offers a vast alumni network due to which placements percentage is high. Also being 100 years old institution IIT BHU has well-established labs with good equipment. Whereas, IIT Indore is a new IIT and still developing. According to NIRF Rankings, IIT BHU has a better ranking that Indore: IIT BHU(11), IIT Indore(13).
Mechanical Department is one of the oldest departments of IIT BHU and has many experienced faculties who are experts in their fields. Research culture at IIT BHU is also better than IIT Indore and there is a lab in IIT BHU being sponsored by DRDO for research. The course curriculum for Mechanical is nearly the same at both the colleges. As IIT Indore is recently established (2008) it has modern infrastructure while the infrastructure of IIT BHU is quite old.
Apart from academics, the IIT BHU Gymkhana has lots of clubs and councils like Sports, Science and Tech Council, Film & Media Council, Cultural Societies which boosts personality as well as skills. Also, IIT BHU has 3 fests (Spardha, Technex and Kashiyatra) that witnessed the participation of students from over 1500+ colleges and schools and top motivational speakers and celebrities.
Regarding placements stats of IIT BHU, top companies, and government organizations like DRDO, ISRO, IAF, Maruti, Bajaj, L&T, BHEL, HUL, IOCL, etc. visits campus for recruiting students. In 2019 a total of 109 students got placement from Mechanical Engineering with average salary package ranging between 10 LPA to 58.21 LPA. The average package offered in IIT Indore was around 16 LPA. Placements of IIT BHU has an edge over IIT Indore.
So, overall IIT BHU Mechanical is better than IIT Indore Mechanical.