1) Wordpress might seem like just a blogging engine, but this is not how the WP developers see it -- on the Wordpress .org About page, it's described as "[Wordpress] has evolved to be used as full content management system" (sic). So they expect people to use it as a CMS. 2) Plone, unless you have a lot of technical chops, is a nightmare to use and maintain. My SO had one set up for her non-profit less than a year ago and they've had so many problems with memory, weird WYSIWIG bugs/behavior (stripping all sorts of tags, including nobr, for one), confusing configuration, costly and/or poor quality plugins, frequent need to modify source, etc that they're looking to move off it ASAP. So I wouldn't recommend it if you're setting up an instance for non-technical folk.