M.Sc

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.