Sorry, rephrase, "I doubt it if they're more difficult for you to administer."
Being an Integrator and a certified engineer for both 2k3Ad and RHEL3. I can tell you that the difficulty in administering depends on several factors.
1) System Knowledge, every system has its gotcha's. If you know them a set up system will not be buggy
2) System Purpose, for the most part youre desktop and desktop infrastructure is much better off on 2k desktops and 2k3 AD. But a weblogic / websphere, database, Mailserver, ... Many of these are much easier to admin, and are more stable and scalable under *NIX.
3) Pre implimnetation Planning..