I've worked with rails a lot over the years, including high traffic sites, and the general comment I'd make is that Rails scales more or less like PHP, but consumes far more ram per process doing so. Beyond that, whether it's good for your project probably depends a lot more on culture and the people involved than any technical distinction. Deploying rails was historically rather clunky, but that's been resolved over the last couple years thanks to folks like Heroku.