The Node.js ecosystem has a lot of potential, but the variety of off-the-shelf add-ons is severely limited compared to either of those more mature frameworks.
If you think Node.js is easy, you've never really experimented enough to understand what makes Rails so effortless. It's a lot easier to produce a production-ready application with Rails than it is with Node.js as it is today.
In four years, as Rails starts to add less critical features, Node.js may well have caught up.
Pro tip: Don't put this on your resume.
For those that love to build things from the ground up or to carve out new solutions, Node is a great place to be. I think it's got enormous potential and is biggest opportunity since Python and Ruby took off around years ago.
Just don't think because you can create the same sorts of apps with Node that it's as easy.
Ruby on Rails even three years ago was laughable compared to today's toolset. Node is catching up quickly, covering ground faster than Ruby ever did, but still lagging.
I think in the long run Node will beat the pants off of Rails but it's going to take an enormous amount of work to make that happen.
The missing 5% is mostly things that make your development process more effortless.
I've found that it's easy to get a first cut of an application out inside of two weeks with Rails, but you will probably need more time or lower expectations when working with something more limited like Django or Sinatra.
Since Rails imposes a lot of conventions, applications are easier to organize if you follow the rules. Sinatra is far more open to interpretation, so if you're not disciplined it can turn in to a bit of a mess.
I'm a big fan of the DRY principle and it's much easier to apply within Rails than in other environments. A lot of this relates to how Ruby is a lot easier to meta-program than other languages.