I find DW to be much easier to use, but then again I had a job where I was paid for maintaining a few such wikis. Nowadays I maintain two for my own worldbuilding (with plans on a third).
That said, most of the stuff that's easier on DW is for technical kinds of documentation: code, tables, statistics, information that has a relatively linear organizational structure. The plugins and themes help a lot and they should not introduce future maintenance issues (unless your system undergoes an unplanned webserver or DW upgrade, which it should not be doing except for security fixes). For a project that has more art / creative assets, or very specially for a project that would require three- or four-dimensional connectivity of concepts and items, I'd defo use something like Mediawiki instead.
Something like "looks dated" is mostly subjective and most of these platforms do allow things like themes for customization, so that's not really much of a variable for me. Whether you can easily access the platform's tools for editing and managing is more important, and on that sense my understanding is that Bookstack's search and indexing are better than DokuWiki's, if mostly because DW does not have built-in tagging and its search system defaults to requiring globs for fragmgemts / partial searches. On that end, if your users have expressed that it's easier to find the stuff on Bokstack, and editing- / publishing-wise is all the same to you, I'd go with Bookstack to make your work more approachable for them.