This is just a proposal, try to explain a bit my views about why Tikiwiki is a better choice than other alternatives and can be integrated/copied&pasted to the Why Use Tiki page,
Integration between several information types
With Tikiwiki, there are several ways to publish information. It alone gives articles (postNuke), forums (phpBB), image galleries (Gallery, Coppermine), blogs (WordPress), wiki pages (phpwiki, MediaWiki), etc. Those features are integrated in one unique package where resources from one kind of publication can be used/included/etc in others, and the interface can show modules belonging to all to show news specific to them, samples, rankings, etc.
Tikiwiki could or have not the top features in each of the previous categories, but is the top (the only?) one integrating all of them, and a lot more.
You can mix several of the previous examples of separate applications, but only with Tikiwiki you have an unified administration, login, user base, theme, way to work with it, etc. Mixing separate packages sometimes produces sites where you must login twice, or go to a complete different screen/modules/menus/etc to perform a task/see something, etc, the body of your site would be separate parts of different bodies barely tied together.
Granular permission system
In several wikis, at most you can decide if registered users are editors and not anonymous, and the same happens with most of the applications showed before. With Tikiwiki, you have user groups, each one with its own set of permissions related to each information kind. You can decide not only what groups can edit i.e. wiki pages, but also what ones can rename, what ones can delete, and so on. An admin for a section don't need to be for the entire system.
This permissions control a bit how the site looks, each one of the menus you can build can depend on the permissions/groups of the viewers. The default menu shows only the options that the current viewer can access, and modules could depend on the user group too. Also the actions attached to the content (i.e. buttons to edit, delete, etc) also depends on the permissions of the current user.
There are several themes bundled with Tikiwiki, but a site could define its own style sheet and make its own particular look.
But more than that, given the separation between data processing and presentation of the design of Tikiwiki, the way the page is built could be changed, from the presentation of particular data to how the entire site structure looks. This happens because the way the page is show are composed by several templates (a graphical example could be found in MoreNeatLayoutSchema), one that contains most, then other for the side columns, others for the top and bottom of the page, other for the middle section, and inside that is showed the template for the current option that is being executed. There are several "non standard" sites on MosePreferedTikis
There are a lot of other characteristics that make it even better. Is open source, what ensures extendability, programmed in PHP what ensures a wide ranging of hostings that can have it installed, it stores all its information in a database (what helps a lot backups, migration of servers, and is a step forward for clustering), is multilingual (both for the interface and in an increasing way, for the content) and its development is very active (several times ranked between the top most active projects in sourceforge) what insures it a future.