Spring vs EJB

First, let me say it clearly, I'm not saying you shouldn't use Spring but, because you are asking for some advantages, here are at least two of them:

1. EJB 3 is a standard while Spring is not (it's a de facto standard but that's not the same thing) and this won't change in the foreseeable future. Although you can use the Spring framework with any application server, Spring applications are locked into both Spring itself and the specific services you choose to integrate in Spring.
2. The Spring framework sits on top of the application servers and service libraries. Service integration code (e.g. data access templates) resides in the framework and is exposed to the application developers. In contrast, the EJB 3 framework is integrated into the application server and the service integration code is encapsulated behind an interface. EJB 3 vendors can thus optimize the performance and developer experience by working at the application server level. For example, they can tie the JPA engine closely to JTA transaction management. Another example is clustering support which is transparent to EJB 3 developers