Which is better, IIT Kharagpur for CSE or IIT Delhi for maths and computing?

Firstly, there is no right choice as it all depends on your personal preference rather than the Institute. My friend was in a similar dilemma and ended up choosing IITD MCA mainly because it was closer to his home than Kharagpur. So a certain Institute can be a good choice for you but not for the other person. It’s better to talk to people from both the institutes and determine which is a better option for you than comparing the institutes based on data.

• Faculty: Some professors surely are weird or you can say over rigorous but such professors can be found in any department be it CSE or Electrical. On the bright side, there are some very cooperative and learned professors who teach their subjects so well, people fall in love with their subjects. 
• Curriculum: The curriculum is quite a good one introducing you to a lot of areas in theoretical and applied Math like Topology, Linear Algebra, Probability etc. Most people who claim to have been Math lovers realize that they haven’t really been introduced to the world of Mathematics until now.
• Alumni: IIT Delhi has many alumni working in finance and tech industries while some are even leading such industries. This guarantees a high paying job to a certain extent provided that you have maintained a good GPA. 
• Campus: IIT Kharagpur is located in a very location and is so huge that it makes commuting a difficult task. IIT Delhi on the other hand is located in the center of the city with many places to explore nearby. Again, I will suggest you make an informed decision after talking to people from both the institutes.