Both the colleges are really good and come with their own tags. In one, you will have the NITian tag and the other will give you a BITS tag. In the end, you will have to make a choice between the branch and which one you like more.

If you are interested in coding and electronics, ECE will be a good fit for you. If you are good with fluid mechanics, thermodynamics and like hands-on work with machines, mechanical is another really good option.

With ECE, you will probably end up working in core firms that are IT-based. You should figure out what kind of life you are looking for and what field you want to study.