See this are a very complicated judgement which differs from person to person.

Now , the basic way of judgement is you should be wise enough to select whats your preference. If you want to do scientific research in computer science or computer application go for phD. PhD needs a lot of time and perseverance , so you should judge it then only take the decision of phD.

If you want to specialize in specific area and want to be industry relevant. You can go for MTech.

This is a very rough approximation. So you should be careful enough to select the subject as per your career goal.

I hope my answer helps you. All the very best for your future endeavors!