I'm looking at architecture solutions for a mobile project that will have a web-service/app in addition to native apps. I've been looking at various libraries, frameworks, and stacks like jqm, backbone, parse, and meteor. Meteor, sort of an "open stack package framework", is tightly bound with node.js.

There is a lot of talk about the benefits of using the same language both client and server side, and I'm not getting it. I could understand if you want to mirror the entire state of a web application on both client and server but struggling to find other wins... Workflow efficiency?

I'm trying to understand why client/server language parity is considered to be a holy grail, any explicit examples or links would be greatly appreciated, thanks!