I think the question these days is what's best for implementing a REST interface for a Javascript client to hit. I prefer Java largely due to #1 & #3 above but also because it seems like there is a more well-trodden path to performance and scaling.
Kind of disagree on your PaaS point. I can deploy Java in App Engine for example.
Node is great. TBD whether it's any better on the maintainability and decoupling points than Rails. It's theoretically nice to be able to use the same language for server and client but I'm not sure how much that really matters.