There is no right option as it all is a matter of preferences that varies from person to person. So the answer is generic and can be helpful for someone who hasn't yet decided on a branch. My preference order will go from the safest to the riskiest option.
Pros
Cons:
This branch is highly suitable for those interested in both CS and Mathematics. This option is safe in the sense that an average CGPA might get you a non-core job while a good CGPA then this branch has a high employment rate and will work in your favor. Its graduates are highly demanded today.
Pros: You get the chance to pursue the most coveted engineering branch at an extremely reputed institute.
Cons: You will suffer a lot if you are not able to meet the performance standards of the branch. Moreover, you will have no option to go for Finance roles or higher studies which most IITians who are unable to do well in their core branch do.
Thus we can conclude that being an IITian guarantee more success mainly because of the tag and the vast options available.
The pros of each branch above can be considered to make a more informed decision.