there exists reasons and needs for which
weblogic could be prefered to orion, which clustering many app. servers
(which is very rare but sometimes very important and reqired) is one of
those reasons.
I accept (as far as i know) that weblogic  is of the best (if not the best)
in clustering ....
But are you going to forget performace!!
It's not wise to confuse different capabilities of different app. servers.
I mean we need to consider our needs and constraints. Do we really need to
use clustering capabilities of weblogic and pay 10,000$ for each processor
in addition to 35,000$ which we pay for the app. server.
BTW, orion lacks clustering on ejbs  but oracle has enriched oc4j  with
such capabilities. Oracle is a big company and i hope they do a nice job,
but i've never read any article or spec. about oc4j's new clustering
features.