I haven't used neither of the mentioned wikis, but here are some interesting links that you might take a look at.

http://www.wikimatrix.org/compare/DokuWiki+PmWiki
http://www.abcseo.com/blog/dokuwiki-vs-pmwiki
http://www.wikimatrix.org/forum/t539-dokuwiki-pmwiki

Cheers :)