Which is better: BITS Pilani Hyd mechanical or VIT Vellore CS?

Rather than focusing on the institutes, it’s best to give importance to your branch. I know a friend who gave up on BITS Hyderabad Mechanical production for core Mechanical at VIT. When I asked her the reason she told me that for her it was the branch that mattered more and VIT offered the branch of her choice.

So I will advise you to do the same. Analyze where your interests lie and choose the institute accordingly.