Why I wouldn't use Rails for a new company
blog.jaredfriedman.com
blog.jaredfriedman.com
It's important to note that Express, the most popular Node framework, is a clone of Ruby's Sinatra, not of Rails. That's a great back-end when your front-end is iOS or React and you have a relatively simple data model. But it's not as strong a solution if you need to do server-rendered pages (which we need to support IE8).
The bigger issue is that Rails is just a much more mature and full-featured framework than Express or Sails.js (which is designed to be Rails for Node). From migrations to validations to strong parameters to many other areas, Rails just offers a ton of back-end functionality that is not as mature on Node frameworks. The big question is how much back-end business logic needs to be implemented.
I haven't run into any issues with Ruby's server performance. AWS instances are easy to spin up, and any Ruby compute time is almost certainly going to be overwhelmed by network and database access. The performance we're focused on is developer productivity, and I think Ruby retains an advantage there over Javascript (though obviously we use both). If I were trying to support millions of simultaneous web socket connections, I would almost certainly go with Node (or maybe Go).
My understanding has been that Node web dev frameworks are still difficult to use for larger projects. Perhaps this has changed in the last couple of years?
On an unrelated note, Google search trend charts always struck me as poor tools to judge popularity of technologies. For instance, here is a chart that shows "javascript" search volume dropping from 94 in 2004 to 24 today: https://www.google.com/trends/explore#q=javascript
For a new company, pick a scripting language you are most comfortable with (if it's php, pick your next best language). Then pick the most active framework from that pool. You can never get to the end of a rails vs whatever debate so just go ahead and pick a framework you will enjoy working with.
The key thing for me was that using something else let me learn a lot about the request cycle while Rails seemed to try to abstract everything away.
I became a better programmer by leaving Rails.