BITS is known worldwide these days for its academic culture and its off-the-charts placements. According to some of my friends studying there, M.Sc courses are some of the best courses available in BITS and all its branches.
M.Sc in physics, chemistry, or Maths won’t certainly give you the placement you wish for but it will still be good. Placements in M.Sc PCMB are great when the student gets CSE as the engineering branch in the next few years. Also, M.Sc in Economics is very good when it comes to placements and does not depend on the branch you will be getting in the 2nd year based on your CGPA.