It depends on your knowledge and time. I'd recommend ES6 for better understanding of JS (although TS can do the same). TS is a superset of ES_ so the argument is confusing. I'm guessing this is more so to do with if you want to have a strongly-typed environment versus standard js. If you have limited time TS, but for better understanding of your code (knowledge aspect) I'd recommend ES6. The syntactic sugar and type enforcement can be a hindrance in understanding the double edged sword that is Javascript. You also still could just write ES6 in TS and have both.