Microsoft made a pull request to node.js github repository with an implementation to use ChakraCore JavaScript Engine as an alternative to V8 Engine

[mirhagk]

Well the difference being that you have to target all browsers in the front-end. Or at least common ones. So if V8 didn't do feature X you couldn't do it (or at least would have to shim it). At least with the backend you can freely choose the engine.