HI deepti,

First of all, focus on college comparison after you clear entrances.
For the sake of answering, there are many government colleges which are no comparison to BITS Pilani. Placements are better in BITS as compared to any NIT but top 3 NITs are also really good colleges. besides bits and iits have almost same placement opportunities. Academic system of BITS is best in India (better than  IITs). Social life is almost equally the same in Bits, Nit,IIT (except IIT Bombay which has best personality development opportunities). Why do you care for alumnis?? From branch point of view every college is different. For example, MNIT jaipur is best among NITs for mechanical engineering. IIIT Hyd. is best in india for CS !
Campuswise IITs are best, some NITs are good, BITS goa is also good, BITS Pilani is under renovation !
Moreover, it depends on you how you want to shape your personality !