First of all Bits Pilani and BIT Mesra are 2 different colleges , BITS Pilani take admission through Bitsat whereas students in BIT Mesra come through JEE Mains
For BITS Pilani most of the btech branches have very good placement records and surely some of its courses comes in league of Top IITs
Whereas BIT Mesra too have decent placement and records specially placement and packages for CS/IT are great and it comes in league of middle NITs for sure
Both colleges are good enough although when you are asking questions like this please mention the branch you are going for as placements differ lot by branch you take for the same college if placement for CS is 20lakh avg and for the biotech it may be 4lakhs so they vary a lot