One of the things I hate about MediaWiki is that you have to use those [[Category:name]] (name is a placeholder of the category's name) links at the bottom of the page. In Drupal, you can enable tagging (makes an AJAX field for tagging; searches for existing tags), multi-select or select from a drop-down list. This could be complicated if you have to categorize/tag the article a lot of things. You couldn't simply copy-paste a comma-separated list into a MediaWiki article, but have to put those category links at the bottom of the article. This can be confusing because MediaWiki also uses the square brackets ([[ and ]]) for both internal links and "inter-wiki" links too. Also, there is no tag cloud extension available for MediaWiki.
Wikipedia has long been discussed about their No Original Research (NOR) policy being a violation of their own Neutral Point Of View (NPOV) policy. Recently, a user complained about the "excluding tiny minorities" rule. Personally, I disagree with this complaint because: