hey,
Actually your question is not quite clear..
You just cracked JEE and you're thinking of going to NIT allahabad...i do not anticipate that
anyways
I think you are pretty much confused between Mechanical at NIT Allahabad and Aerospace at IIST
My suggestion is that you go by your interes here. Aerospace is all about designing aeroplanes or shuttles in few casses if you are really thinking of going that far.. Aerospace actually has a very little scope in India. If you plan to go to foreign and especially countries like USA france germany or Russia, this is best suited for you.
As far as mechanical at nit allahabad is concerned, is also a good branch. Has a very wide scope across the globe. But the main problem that always come with Mechanical engineering are the hardships that one goes through during his stay at the college. Chose this onlyu if you think you are really capable of working just not hard but the hardest...
Best of luck
