BIMTECH retail management is not a very well known course. If you are very sure of making a career in this domain then go for it. Also, look at their placement reports and talk to someone who has done the course. If you are not sure which career path you want to set out for, then go for a core program. Also, if you can afford a year, prepare for CAT 2020 and don't settle for anything less than new IIMs, given the pandemic situation. All the best!
Bimtech retail management would be the good option only if your future aspects or say interest level more towards the retail sector. As after getting into retail field it would be tough for one to get into core marketing. Retail is tough job and it’s not everyone cup of tea, so better compare all available options before moving towards retail one. Marketing students have option to apply for core or retail, however, it would be tough for retail one to apply for core marketing. It’s just like doing internship in supply chain management and applying job for marketing.