Yes, it was confusing once, two years ago and now I can happily confess that I do not regret choosing IIT Gandhinagar over BITS-Pilani. Since I also have friends in both the colleges, I can provide a detailed overview of the good and bad aspects of the colleges.
Also, information on BITS might be limited due to it will depend mostly on other people’s experiences, but the answer will talk about the good and bad side of Mechanical Engineering at IIT Gandhinagar.
Following are the merits of IIT Gandhinagar:
One thing that students could miss at IIT Gandhinagar is the cultural fests and events. They don't have grand cultural fests of their own. This privilege was taken away by the seniors, which we were trying to rectify. But gratefully, we already have enough, so, that doesn't make us expect too much of these grand fests for ourselves.