Hello student, 

Both of the colleges are excellent for any branch aspirants among Kolkata engineering colleges. 

I would suggest you to choose IEM among the two if you are interested in engineering only for your education and placements. In that regard, IEM is ahead of Heritage. IEM is very strict and treats their students almost like school children with their strict timing. if you are even late by a minute you can bid the whole day goodbye. 

However, if you want a complete college experience including the fests, heritage will suit you better. They offer good placements too and arrange superb fests to give you a co-curricular opportunity as well.

Cheers!