EJB 3.0 entity beans are modelled after Hibernate and other POJO-based ORM solutions, and the Hibernate team was deeply involved in writing the new spec.
And, of course, in JBoss, the EJB 3 persistence implementation is just a very thin wrapper around Hibernate.
At a high level there is very little difference between using Seam with Hibernate or EJB3 persistence, though obviously Hibernate is more feature-rich.
Thanks for the quick reply! If I needed (or just wanted) to use Hibernate, could I still use session beans with Seam? Is it all or nothing?
Of course, you can inject a Seam-managed Hibernate session into a session bean. Or, when running in JBoss, you can get the underlying Hibernate session from the EJB3 EntityManager anytime you like.