Danger on Ruby is more mature, has a solid plugin eco-system and is very stable. It supports Ruby 2.0 and above, and will likely work on any CI setup without additional work.
The project is on version 5.x with about a hundred releases, that’s a lot of battle testing. I consider it in a great place and is unlikely to have breaking changes from this point onwards. The GitHub issues to number of downloads is really healthy too. Almost 10 million downloads now and a new issue maybe once a week.
I have no intention of ever deprecating Danger Ruby. If you’re using it today, you’re fine to stay that way.
Get started with Danger on Ruby.
In re-creating Danger in JavaScript, I built it with a larger scale in mind.
Danger JS has its own plugin eco-system and is doing a bunch of things the Ruby version cannot (like Peril and separate language implementations). Danger JavaScript probably has everything you need.
If you’re working in a Node environment this is definitely the right choice.
FWIW, I find it easier to work with JavaScript Dangerfiles because they have TypeScript annotations.
Get started with Danger on JavaScript.