Hi,

It all depends on your interest, if you feel that structural engineering is good for you and you interested in pursuing your Mtech with this branch then surely go for the IIT BHU, but if you like geotechnical engineering then stay in IIT Kharagpur. Because both the colleges are very good and the placements are also very good. 

So I hope I was able to clear your query

I wish You best of luck

Thank You