SmartGWT 4.0 ,client-side integation

I am a newbie to the SmartGWT 4.0(especially the client-side integration ).I am developing an application using spring/JPA2,My business logic is based on the GWT-RPC.
I've read the quick start guide,and i've seen that the best approach is to use "RestDataSource" so my question is which is the best way to integrate the smartGWT-client side?
Should i consider the "GWT-RPC DataSource"?or moving to the REST approach using the "RestDataSource"? is there any other appaoch i can consider ?
Note:Can you point me to any usefull tutorials?
Thanxs in advance.