As per my idea both IIT institutes are best for you. Both Iit Mumbai and Iit Kanpur are top ranked institutes.

IIT Bombay is well-connected to the rest of the country as well as the world as compared to IIT Kanpur which lies in a tier-II city of India.

And it is a known fact that living in a metropolitan has perks of its own.

Apart from this, the former engineering college also lies in the financial capital of the country which has benefits of its own.

Comparison:

Indian Institute Of Technology, Bombay Indian Institute of Technology, Kanpur
Rank 1 3

College Preference 73.41% Over IIT-Kanpur 26.59% Over IIT-Bombay
81.77% Over IIT-Delhi 56.73% Over IIT-Delhi
Type of College GOVERNMENT (IIT) GOVERNMENT (IIT)

Exam IIT JEE IIT JEE

CS Opening/Closing Feb-93 46-317

ELEC. Opening/Closing 1-106 45-556

India Today Rank -NA- 1

Outlook Rank 3 4

Dataquest Rank 1 -NA-

Student Intake (2011) 880 827

Fees (LPA) 0.801 0.89