Just go with openjdk* where all future development will take place. Beware though that javavmwrapper no longer respects /usr/local/etc/javavms but relies on /usr/ports/Mk/bsd.java.mk which for some reason (which is beyond me) always favors Diablo. Hacking /usr/ports/Mk/bsd.java.mk will help until the next # portsnap fetch
so your best option is to make use of the JAVA_HOME env variable.
# setenv JAVA_HOME /usr/local/openjdk6
will do the trick. Also i have the slight impression that jboss starts a little more faster in my 8.0-RELEASE-p2 amd64 with OpenJDK than Diablo.
Another note, be aware that Diablo is compiled for FreeBSD-7.* hence it needs the COMPAT_FREEBSD7 kernel option.
Anyway, the recommended port is Openjdk, followed by native jdk, followed by Diablo. I have never run the linux-sun-jdk16 port, and i doubt people have been relying on a linux jdk for quite some years now.