Dear Pratistha Chatterjee,
Unless one is firm, choosing a stream for specialisation is confusing. It happens with many.
Marketing, HR or Finance all the streams of management science are dynamic. Therefore, your success will depend not on the choice of the stream but on how much knowledge you absorb in your MBA course. Your choice should be apparent by your behaviour or how you carry yourself. Above all, your academic excellence will also have a bearing on your career's success.
Whatever the specialisation in the MBA may be, the common factors that make one successful are communication skills, business writing skills, fluency, command of English, critical and creative thinking, comprehension abilities and so on. Knowing the subject is one thing but how one presents the knowledge is also important.
Otherwise, look at this very forum. Some seniors just pass the comments without reading the replies from other members. They can't write a few sentences on their own! So whatever your choice may be, please don't be one among them!
My personal opinion is that among the three, Marketing is better. Not that it is more vibrant than the other two. However, many MBAs prefer chair-centric work. On the contrary, the marketing professionals need to be on their toes. Preference for sedentary work by professionals from the other two streams reduces the competition for marketing professionals. While recommending so, please note that I wish you to choose hardcore marketing and not become a lifelong salesperson!
All the best!
Dinesh Divekar