SVR4 (hence SunOS 5.x) tries to make everybody happy. The
traditional (slow) System V "shutdown" runs all the rc0.d/*
shell scripts with "stop" as the argument; many of them run
ps(!) to look for processes to kill. The UCB "shutdown" tells
init to kill all non-single-user processes, which is about two
orders of magnitude faster. In old versions of Solaris (2.2 and
before) the UCB version did everything it should except actually
halt or reboot.
If you run a database (like Oracle) or INN, you should
install a special /etc/rc0.d/K* script and make sure you
always shutdown the long way.