Hwllo Aspirant..

First, let's define these concepts.

1. AI is like root of ML(Machine Learning), DL(Deep Learning).
2. ML is the sub part of AI.
3. DL is the sub part of ML.
4. Data Science is neither fully cover AI nor it is AI, It is the part of AI.

Many companies (both product and service focused) are looking for persons with various profiles these days. You can't declare, "I know only ML, DL, or Data Science." You need to know something about all of them, as well as the basic understanding of the major field for which you were hired. So, based on the foregoing response, it is evident that all of the fields you named have a brighter future.

Choose any of the fields that appeal to you. Every field has an equal chance. I recommend that you attend plenary sessions, read research papers, and try to foresee what future wants might be so that you might design the next ground-breaking product or plan for your future career alternatives.

I hope this information is useful.