Here are roughly summarized the key differences between RESTful and RESTless web services (it does not have to be strictly valid):
————————————————————-
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.

Here are roughly summarized the key differences between RESTful and RESTless web services (it does not have to be strictly valid):
————————————————————-
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.