b2evolution also makes a good impression on paper. It's surprising how far all these blog programs have come while you're not looking.
In any case, b2evolution makes a very good showing when it comes to antispam and security. And it also seems to have good XHTML support and a plugin architecture. The plugins are divided by purpose (Edit-Plugins and Toolbar-Plugins). I think the somewhat simpler form of plugins in WordPress will be easier for many to understand, but programmers will probably prefer b2evolution.
Personally, the admin environment is a bit too playful for me - though I only looked at it in the online demo. Also, the standard template doesn't look as clean and tidy as WordPress's - I think with the latter you have an easier start to impose your own layout. What's definitely nice is the choice of input parser for posts - I've done something like that in the Python Desktop Server too, precisely because you don't always want to have certain plugins active. Otherwise, it's of course very similar to WordPress - it's also a b2 descendant. WordPress probably has better support for images since it can automatically create thumbnails. Also, b2evolution lacks the metaWeblogAPI. On the other hand, what's nice is the integration of referrers and search engines directly into the blog - similar to the evaluation that the Python Community Server does for me. The usability design of b2evolution seems a bit confusing in places: permalinks to posts are small chain symbols, permalinks to comments are small document symbols. It's also somewhat inconsistent in other places.
Conclusion? If I can draw one at all from this mini-test, I'd say that for me, b2evolution implements just one small checkbox, switch, or option too many for most features. Therefore, I would personally lean more towards WordPress - I can imagine the code is somewhat simpler in structure and therefore custom hacks can be integrated more easily.
In terms of function, however, b2evolution clearly wins on points. Whoever prefers lots of features and likes to draw from a full well, or who wants to venture beyond normal blogs more strongly into the CMS area, will certainly be thrilled with b2evolution.
What I don't understand with either b2evolution or WordPress: neither of the two projects implements stories. That is, article formats that are not fixed to the calendar. Sure, you can realize that with a category or with a separate blog (with b2evolution's multiblogs functionality certainly much easier than the category hack needed for WordPress), but I find it impractical that you have to go to such lengths just for an imprint...