Well it all depends on your interest and future plans. I'll summarise the possible scenarios.

If you plan to do a job after B. Tech then mechanical engineering does not provide you with many jobs (except at top colleges) and you'll have to work in an IT firm only.

Another viewpoint is if you plan on further studies then specialisation in mechanical engineering is a good options. There are many job prospects after post graduation in the field of mechanical engineering. So if you intend to do further studies in this field, then you should definitely take up mechanical engineering.

Thirdly, if you intend to do something like MBA, Designing etc after B. Tech then your branch does not matter very much. You can take any branch you want. The only requisite would be you B. Tech degree. Branch can be anything then.

In case you don't have future plans or thought anything yet, then it is advisable that you choose the branch of your interest otherwise engineering will feel like a burden and you won't enjoy studies.

Hope I've solved your query.
Feel free to ask any doubts. :)