Transaction handling in Websphere Application Server 4.0

[Victor Su]

Sub.: Can we replace the BMP Entity bean with the Session Bean by using the JTS features provided in the new Websphere Application Server 4.0 environment?
Dear all,
I am currently reading how the JTS manage transaction behind the scenes of WAS 4.0 EJB container.
I have the following questions if you guys could give me the advice:
As in the latest WSAD 4.03(Websphere Application Developer) IDE tool, we can set the transaction context for EJB (whichever entity bean or session bean) and the J2EE container can create transaction-aware pooled DataSource objects and takes care of the transactions being carried out within the same transaction context, can we simply use the Session bean to replace the BMP Entity Bean? (as we can use UserTransaction.begin() or .commit() wrapping around the transaction method in the Session Bean)
Please note that the BMP Entity Bean would consume more resources than the Session Bean, since the WAS4 provides the transaction monitoring context and auto-roll back features for us, why do we still stick onto the entity bean for communicating with the database?
Thanks for your suggestion.
Victor