`Helper`s are generally used for view related purposes (in my experience), for things such as simplifying view logic or generating a piece of html that for whatever reason you have decided isn't large enough to be a partial. `lib` models are generally for shared business logic (in my experience). I personally find using a class in `lib` easier, too. When I see `SomeClass.method`, I know it's going to be (should be) in `some_class.rb`. PromDash is a simple enough project that it wouldn't be hard to find a method in a helper, but in larger projects you may end up including multiple modules into a model, in which case you have to ack for the method name (if you aren't using `ctags`, I guess) and find the definition.