Which college has better placement: IISC Bangalore or IIT Bombay?

It's highly illogical to compare 2 of the most prestigious technical institutes of the nation especially when both institutes exist to serve different purposes. IIT Bombay or any IIT in general was established to produce the finest engineers who would contribute to the development of the country, whereas IISc was primarily established to conduct core research. Both of them are contributing to the economy of the country in their own way and are India's biggest assets. 

IITians usually prefer working in big MNCs and earning hefty packages while IISc students have a strong commitment towards research and scientific achievements with money and job as secondary aspects. They have a rather simple lifestyle with packages if not better at par with IITs. The level of satisfaction is high as they are doing something they are passionate about without worrying about money.

Another major difference is that the IITs flagship course is usually BTech while IISc being a research-oriented institute, has only. MS or M.Tech (graduate)IITs have a huge batch size with many UG students getting specialization in different engineering fields while IISc only has limited seats for those who are willing to work towards high-end research.

IIT Bombay is a great choice if you prefer a stable lifestyle and have no or little interest in research. Here you will get the opportunity to serve the nation by becoming an ace Engineer, Entrepreneur, or Executive Officer in any big company. It's true that IIts offer diverse opportunities whereas in IISc your goal is almost set.

However, if you prioritize research over money, then IISc will serve you best.  The high-tech labs and research work open gates for tio foreign universities. So choose what your passion says!