1. Protocol RESTful services use REST architectural style, RESTless services use SOAP protocol. 2. Business logic / Functionality RESTful services use URL to expose business logic, RESTless services use the service interface to expose business logic. 3. Security RESTful inherits security from the underlying transport protocols, RESTless defines its own security layer, thus it is considered as more secure. 4. Data format RESTful supports various data formats such as HTML, JSON, text, etc, RESTless supports XML format. 5. Flexibility RESTful is easier and flexible, RESTless is not as easy and flexible. 6. Bandwidth RESTful services consume less bandwidth and resource, RESTless services consume more bandwidth and resources.