Between IEM Kolkata and SOE CUSAT, the former is the better choice for CS. I have a few friends at IEM Kolkata so I can give you some information about their CS department.
Cutoff: In West Bengal, IEM is one of the oldest private engineering colleges. Despite being a private institute the opening and closing rank for CS at the institute is quite high. According to the trends in recent years, it is around 1500.
Placement:
Coding Culture:
The campus has a great coding culture. In recent years many students cracked TCS CODE VITA. Also, two teams qualified for ACM ICPC for 2017-18 regional.
Entrepreneurship:
The college organizes various workshops and events regarding entrepreneurship regularly.
Fest:
IEM has two fests, i.e. Tech fest (Innovation) and Cultural Fest (IEMPACT), you will get a lot of exposure through these fests.
Considering all these factors it is safe to say that IEM Kolkata will be a great choice for a CS degree.