Hii aspirant..

First of all congratulations as you have performed quite well in Wbjee exams and getting some good college for admission. 

Both IEM,  saltlake and HERITAGE are the best private colleges under WBJEE entrance examination. Both are very good and if we compare then both are good from onr another in many ways.

If you want college life and infrastructure then surely Heritage institute of technology is having an upper hand over IEM , saltlake. But the placements and faculty at IEM , saltlake campus are better comparatively. 

And if we rank both of them then IEM is always considered as having upper hand. 

Coming to departments then the placements of CSE and IT departments are almost same in both of these colleges. Because maximum placement is offered by IT companies offering jobs to both CSE and IT department students. 

Hope it helps. 

Best of luck for your future .