Should I choose mechanical engineering in IIT-D or CSE at NIT Surathkal?

Both Mechanical and CSE are good branches and offer ample placement opportunities. In this case, you should choose between the colleges.

IIT Delhi is one of the top Engineering colleges in India. They have the finest faculty, and IITD alumni have the highest number of unicorns in India. With an IIT tag, you can easily grab a job in top MNCs. Being an IITian opens great opportunities for you to pursue your higher studies at US/European Universities. 

IIT Delhi Placements are top-notch. Even its Mechanical branch records an average salary close to 12 LPA. Several Finance, IT, and non-IT MNCs are open for every branch during placement season at IIT Delhi. So, you can switch to an IT career later on. For UPSC/GATE aspirants, Delhi is the ideal location. 

CSE is a more in-demand branch at present. However, IIT Delhi offers much more opportunities to its students than NIT Surathkal. Therefore, I would suggest you choose ME at IITD rather than CSE at NIT Surathkal.