posted 8 years ago
React apps are typically written using ES6+, though nothing prevents them being written in ES5 (if you like wordiness) or even TypeScript.
Angular apps are typically written in TypeScript, but similarly they could be in ES as well.
I choose the language that the framework's general community uses as that's what tutorials, blogs, npm packages, and online questions are most likely to be using.
Babel, while essential in the toolchain, doesn't really factor into the choice.