M.Sc

You are qualified enough to seek admission in any specialisation based on your interests, preferencds and personalality traits. Marketing could be a right choice for you if your comm skils are good and if you are an extrovert.

After your M.Tech, your entry cadre will be that of Assistant Professor. You can make a career progression to Associate Professor and Professor later on with experience if you have a Ph.D.

There is nothing called best. All depends on your student-institution relationship that requires a good amount of dedication, smart work on your side & good study environment on the other side. So, I'll suggest you to check your comfort zone, study environment of institution together then make a wise decision.