Actually, one thing I think is horribly overlooked in all the comparisons is the ease of upgrading, having lived through a Moodle Upgrade and just upgraded my MediaWiki. Often you need to be a guru to follow the upgrading instructions and as you mention in your post above WordPress seems to significantly update every 6 months upgrades are needed often.
(and who wants to be stuck in the dark ages when everyone else is on the latest release – with all the bug fixes).