> Here are Ruby and Rails measured against Node.js, the popular JavaScript framework.
> Finding the next Rails or Node.js
This is nitpicking, and it looks like you understand the difference. But in these sentences you are comparing a vm+framework(ruby rails) against another vm(node.js).
The thing is there is no rails for node only a bunch of contenders[0].
js gained its traction with humankind putting a vm in your webbrowser on every machine.
[0]: http://nodeframework.com/