Hi,
Why don't you consider doing a PhD? There are ample opportunities to work towards a PhD degree with scholarships in India and abroad. You can go through the web pages of universities abroad and find a professor who works on a field of your interest. You may contact him/her/them through email. You have to make sure that you have gone through their recent research papers and gained an understanding of their area of research. If you have questions/doubts on their work, much better.

Regarding the courses you mentioned, both are good. You can option for either of them. All the best,

Suresh