EJB versus RPG/COBOL

In Don Denoncourt's book titled "iSeries & AS400 -
Java at Work", he states the following...

"I see two alternatives when using Java for AS/400
applications: one is to use RPG/COBOL for your
business logic, and the other is to use EJB. In either
scenario, you'd use JSP and Servlets to handle the web
interface."

I am designing a server side app, that will reside
completely on one single AS400 machine. This
application may be accessed by up to 500 users. This
is the first time I design a Java app for an AS400, so
I am considering all the choices. Does anyone know
what the pros & cons of the two alternatives
(RPG/COBOL vs. EJB) that Don Denoncourt mentions are?
My main concern is performance and speed of the
app/system (I am not concerned about the
cross-platform issue at all in this case). I hear that
java on as400 is NOT exactly lightning fast. Will
using RPG for the Business Logic improve performance?
It sounds like using RPG alleviates the system level
concerns that EJB is supposed to help with (db
persistence, transactin control, scalability, etc.).
It also sounds like using RPG "could be" faster since
RPG does not incur the cost of all the java object
creation & garbage collection. For sure, it would help
with coding of the new system since we have several
legacy RPG developers and no other Java types here but
me.

Thoughts anyone?

Thanks,
Ivan

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