In my opinion server side should be based on Java 6 (i.e. most production stable runtime at this time) So I vote for Java 6 @server-side
A what about client? Client side (& common libraries) may be able to run @ Java 5, A was mentioned,
but I thing this is not necessary - top application (as hornetQ is in my opinion) should take advantage of most current technologies. If there are some significant advantages of basing hornetQ code on Java 6, I should profit from it!
Ara there memory or performance differences when running hornetQ based on Java 5 @ Java 5 x Java 6 runtime?