BITS vs IISC which is better for MSc physics/math
IISc is the best if you have a research acumen and passion. If not go for BITS and settle for a decent paying Job.
Both are better only we can't able to compare it as such but yaah if you compare it in the research field then it will be IISc because it is one of the institution in India which has got the marvelous achievements in the field of research. Eventhough it has the tag of Institute of Eminence as well from the MHRD Govt of India. So I suggest you to go with the option IISc.
All the best