If we compare PGDCM and PGDM at IIM Calcutta, we see that both the courses have the same networking, placements and even infrastructure. 

Now if you compare both the IIMs, IIMC and IIML, there is hardly any difference in the curriculum or even placements. So deciding which IIM to go for depends on your own preferences.

But if you are planning to quit IT then I suggest going for the full-fledged MBA course from IIM Lucknow rather than a system at IIM Calcutta. 

IIM Lucknow will offer excellent exposure and placements and you will end up getting an above average salary package for consulting.