First we should keep in mind that the basic techniques of biotechnology is same for both medical biotechnology and plant biotechnology but in specialisation you get to learn some special techniques applicable for medical and plant background respectively. For example-

for medical biotechnology you will get strong hold on techniques like different kind of ELISA, kind of microscopy, flow cytometry, protein isolation and quantification,etc.

For plant biotechnology you will learn tissue culture, particle bombardment, etc.

Now coming to your question which have more scope, in my opinion plant biotechnology have equal scope in India and abroad but medical biotechnology have low scope in India but optimum in foreign countries like USA. This is keeping in mind you want to join industry. But if you want to continue in research both are equally good. You can even combine knowledge of both as done in production of various animal protein .