The BA course has been recently initiated at both institutes. Without second thoughts, Great Lakes has top-notch faculty who handle the courses meticulously. But the competitor IIM Calcutta makes the discussion more difficult.
The only difference between the two courses is that IIM Calcutta has probably started the BA course because of its flagship PGPM program under the IIMC brand. Whereas Great Lakes BA is another flagship program. So the focus might be better.
Choose IIM Calcutta if you are willing to attach yourself to its brand name for the rest of your life.