Creating and using content types in SharePoint is often considered as the best practice; however SharePoint workflows created for SharePoint 2013 cannot be associated anymore with content types.
This is a very important point to consider if you are moving to the new platform
In MSDN you can read “Unlike previous versions, SharePoint 2013 does not support workflows that are scoped to a content type (SPContentType). However, the messaging infrastructure is extensible, so it can support any arbitrary scope. As a developer, you can set the EventSourceId property on a given WorkflowSubscription instance to any guid. You can then use that EventSourceId value to call PublishEvent(Guid, String, IDictionary<String, Object>), which triggers a new workflow instance of the specified WorkflowSubscription.”
I will illustrate this in a future post.
If you want to get content types support out of the box, you have to create SharePoint 2010 workflows in SP 2013.