The big adventage of the Wiki is, that everyone can edit (almost) everything.
-> It doesnt matter if a creator of the page is inactive, everyone can edit while in forums you basically have to make a completely new post in order to update something.
-> Or the creator is active but isnt forced to update his topic since there are other people who can edit while in forums only the creator of the topic can edit
Also I think its good to mention, that the Wiki is not more outdated than the forums. Both have much outdated stuff (But also a lot up-to-date stuf ofc.!). On the Wiki everyone can at least work on it while forum topics, which get no care, will rot.
I can just advice the Wiki use.
if you plan to do a guide/info thread, why not on the Wiki? You can link the Wiki page in a forum guide post. Everyone who visits the forums can see the Page and everyone can update. Win win.
Did I mention that everyone can edit in the Wiki?