The syllabus of Electronics and Communication at the IITs is very overlapping with computer science and engineering, and as a result, all the companies which come for recruiting from CSE also allow ECE people to appear for them because of their calibre and syllabus, which is not the same as mechanical, as mechanical companies are less in number and are not known for being paymasters.

So, I'll personally recommend you to go with ECE at IIT BHU as it has a very good scope and you'll excel in it. Hope I have answered your question. All the best!