But sometimes we need information about CRM entities not included in the current page-form so we need to query the CRM2011 web services to get more data,create, update or delete records or make other service calls.
Both ways are fully documented in the SDK but if you don’t feel like reading it all i will explain here the easiest way to use both of them and the libraries needed.
The main different for me is that I used Asynchronous calls with ODATA(although u could change the Ajax query type to make them synchronous) and Synchronous calls with Fetch.
A synchronous call will wait until the execution has finished to continue with the next instruction.
Reading some posts about these two ways of querying CRM2011 people comment that the Rest End Point is more efficient but you can only use simple commands (Retrieve,Create,Update or Delete records) while the SOAP end point is a bit slower but lets you make more complex actions(like making service requests).
Both ways of interacting with the CRM2011 Web Services are useful and fully working so i suggest you read both posts and decide which one fits you better.
Have a nice day,