It's not just RoR vs Node.js, it's the eco-system around it you need to think about. This is an interesting read as far as Node goes: http://www.breck-mckye.com/blog/2014/12/the-state-of-javascr...

Use https://www.meteor.com . You want to build prototypes as fast as possible, and meteor enables you to build stuff shockingly fast. RoR is a thing of the past.