Well Both institutes are one of the best institute of india. It depends on your aieee results that in which college you got the admission.BITS provideds the great facilities for the students of the institute as It's a private institute but fee structure of NIT is very low in comparison of BITS . Infrastrure of NIT is very good.Both will give you the best placement opportunities in final year. After the IITs ,NIT Ranked on 6th position.So it depend on you that which suits you more,location wise or financially.