Like you say that you are interested in journalism,first of all find out what is it in the field that interests you the most. This will make sure that you are genuinely interested and want to make a full-time career out of it. Also in order to know more about the career -pros & cons- read up more and talk to professionals,which will give you an idea as to how the industry functions. If you feel that journalism is your 'calling' certainly going in for BMM would make more sense.
Also you can check the syllabus for BMM online, to get an idea of what the subjects are going to look like. BMM is a professional course and offers a good platform to the students who are interested to make a career in the field of Media.
Certainly just graduation is not going to be sufficient, you will have to go for a PG but that will take some time.
Till then keep all your options open.
Hope this helps.
Feel free to write back for further queries.