DataSource is a feature of SOAP UI PRO for Data Driven Testing. This will enables test cases to get feed with diferent samples of test data. This will connect test case to external storages such as Spread sheets. This handles large set of test data and sampling.
Properties is a feature in both SOAP UI & SOAP UI PRO. This is will store the data for single entry/single data format.
Primarily Properties are using for small number of data inputs.
Property Transfer [transferring properties] is a feature in both SOAP UI & SOAP UI PRO. This will transfer data from one test step to another easily and faster. The term data is professionally refers to Properties in SOAP UI knowledge base. We need to use Xpath language to transfer properties and read the properties from the test steps. This will also helps us to transfer values dynamically.
In fact, all these are referred to Data and data transfer however they have their own uniqueness to apply in the test suite. A SOAP UI professional should use these features wisely with their projects to get maximum benefit to the test suites usage. Professional go with short number of data with properties and large set of data usage with DataSource. In fact, we can do the same with Properties but its very tedious and time consuming.
Try to create a Property Transfer and Properties in SOAP UI.
Try to create DataSource in SOAP UI PRO.
Then, you will know the actual difference it makes. Its your call.
Please let me know, if you have any questions
^Best regards