One of my friends studied at Calcutta University, so I might be able to give you some details about it.
Finally, you should keep in mind that other mentioned universities may not be as old and experienced as CU, but they will show a bit of leniency while giving marks. So ultimately the decision is yours, whether you want to study in a reputed university with a strong and reliable alumni network or opt for the easier way out by getting admission to newer institutions.