IIT Kanpur has several advantages over IIT Delhi. A few are mentioned below:

• Unlike IIT Delhi, branch change facility is not restricted to the first year only and one can change branches even after the 2nd year 
•  IIT Kanpur offers an enriched campus life with great relations between students as well as students and faculty. 
• There are no LAN restrictions at IIT Kanpur whereas, IIT Delhi restricts usage of LAN from 1 a.m. to 6 a.m. 

Lastly, once you enter IIT, your branch rarely matters. Your placements solely depend on your CG, your skills, and the efforts you invested throughout. So, go for a branch that matches your area of interest and you are good to go.

The choice of the Institute as well as the branch is specifically based on your inclinations and only you can make the wisest decision. However, some points that will assist you in making an informed decision are

• IIT Delhi is a winner when it comes to an urban location with a lot of exposure and opportunities outside of campus
• Production and Industrial Engineering is a much lighter program in comparison to Mechanical Engineering and will spare you time and energy for pursuing other hobbies or interests or inculcating new coding skills
• IIT Delhi is the best choice for future entrepreneurs as it helps in incubating ideas and Delhi itself is a hub of startups

However, if you are inclined to Mechanical, then choosing production is not wise. Ultimately, more than the branch and institute, what matters is how well you manage your time and learn additional skills.

I will restrict my answer to Engineering Physics and Chemicals only as I know the same only. 

• The major criterion followed at IIT Delhi by all the branches is a well-maintained CG. To secure good placements one has to constantly score a good CG throughout the program.
• During your admission, the department does not play any role but your 85 percent constraint on minimum possible strength does.
• Engineering Physics is a unique branch for those highly passionate about Physics and want to pursue higher studies in the same
• To secure core jobs, one has to move to MTech in Engineering Physics from BTech in Engineering Physics.
• For Chemical Engineering students, BTech is more than enough to secure decent packages and great research opportunities outside India.
• Consultancy and Analytics jobs are offered equally to students of all the departments 
• Engineering Physics graduates usually take up consultancy or IT jobs 
• Chemical Engineering is the most laid-back department of IIT Delhi with very flexible academics thus making it easy to maintain a decent CG throughout. 

I wouldn’t suggest anyone go for Engineering Physics if they have no intention of pursuing it later. Instead, look for other options in BTech and explore your interests.