Hello Rajesh,
Both courses has different contents to go through. You can find the elaboration below:
BCom

A BCom offers theoretical knowledge of subjects and you specialise in one area in the final year. Some colleges have a mandatory internship and also assist in placements for entry-level jobs in corporates. However,  you would do more of back-end work and provide support services to your seniors. Exceptional candidates could expect to do some customer interface, though it is very rare. Invariably, you would hit the glass ceiling and would need to pursue an MBA to progress up the ladder, faster.
BMM

If you are sure that the media is the place for you then this programme may be the way to go. Most programmes focus on electronic media and hence it is important for your institute to have good infrastructure such as a TV studio, model computer lab, movie cameras, a good library, and facilities for indoor and outdoor shooting as well as a community radio station set-up. Placements mostly don’t happen, but an internship could be a ticket to an entry-level position.