Both are really good, mature, battle-tested.
They've their own pros and cons.
If I were you I'll choose NodeJS, because it'll enhance my JS knowledge so that it will help me while developing for front-end! Also, it's easy to hire JS engineers.
But it's just a personal preference
I didn't get your point on why NodeJS is not a fully-fledged website framework! What made you think so? Any features missing from Ruby on rails?
There are companies, that switched from Ruby on Rails to Node.js: