Hello,

According to the current market situation machine learning is the best option. Because the companies working in this sector are huge. Also the future is completely dependent on technologies like artificial intelligence, machine learning. And if you have a good knowledge and innovative mind in this feild there are no bars for salary. 

To master machine learning you will need a good knowledge of python as well. Python is also used in many other applications such as embedded systems,vlsi etc. 

Whereas AWS is limited to amazon and job opportunities are not high in number in this feild.

Hope it helps.