AngularJS : When to use service instead of factory

Question

I still can't figure out when you'd use service over the factory.

From what I can tell factory is commonly used to create "common" functions that can be called by multiple Controllers.

The Angular docs seem to prefer factory over service. They even refer to "service" when they use factory which is even more confusing! http://docs.angularjs.org/guide/dev_guide.services.creating_services

So when would one use service?

Is there something that is only possible or much easier done with service?

Is there anything different that goes on behind the scenes? Performance/memory differences?

Here's an example. Other than the method of declaration, they seem identical and I can't figure out why I'd do one vs the other. http://jsfiddle.net/uEpkE/ 

Answer 1

You should use a service when you get an instance of a function ("this" keyword). And a factory you will use when you will get the value that is returned by invoking the function reference(the return statement in a factory).