Not that I know anything about this sort of thing, but some problems with the OS X side of the review.
1) He used an older version of OS X Server. OS X.2.1 Server is now out, which apparently includes updated and additional admin tools. Faster compiler too?
2) He couldn't turn off the GUI. I was told that you can. How important is the GUI anyway? I can see it making things a lot easier if you don't know what you're doing, but would you really want to have a sysadmin who didn't know what s/he was doing?
I suppose it'd be a good time saver overall though.
In all fairness he did add a GUI to the Linux server too, although it's not a direct comparison. Plus it seems he used the 2.95 compiler for both Linux and OS X.