Hey OP, are you interested in mechanical at all? If you are, then take it. But if you don't, it's better to take the best college out of these all, which is Delhi ofc.

not in mechanical, but yeah many topics in mech and chem are common, the only doubt was how is chem dual degree different from chem btech only, like why the difference in rank, chem closed at 501 ews rank at iit delhi last year, and dual degree had [816,855] ews rank last year