Using "unix:0" or "hostname:0" when the X11 Shared Memory Transport
(SMT) is installed as part of the 1.2.3 X11rte.obj (X11R5) will incur
a penalty vs. using ":0" See /usr/lpp/X11/README.SMT
3.) Is there a significant performance penalty incurred by using
`hostname`:0 as DISPLAY?
Yes! Using unix:0, you are using Unix sockets. These are much faster
than their TCP socket counterparts.