I do not see much difference between forum and wiki in regard of providing help to the users. Both can be configured to provide similar functionality and it is equally easy to implement links to any of those in the application.
The useful wiki feature for online manual maintenance as I see it are
1) Good page version control tracking who has made changes and easy reversion of changes. This enables liberal delegation of edit rights, encouraging all users to contribute to documentation maintenance. In contrast to a forum where topic header edit rights require administrator privileges which are sensibly only granted to a small fraction of trusted users. The inability to directly fix the documentation without believing knowledge justifies being a moderator and existing administrators agreeing will not increase volunteers to maintain forum documentation.
2) Structures, providing efficient generation of lists / contents. The information content is language independent so only needs to be done once across multiple language versions of the manual
3) Language translation and tracking support is more refined, consistent with the wiki focus on maintaining a reference document vs the forum focus on tracking and storing conversations.
The end result is maintenance of a document in a forum is clearly possible. However it will end up being done by the moderators and in multiple languages. Not a problem for an organisation with a document writer. Also not a problem if nostra, rick and reset are comfortable writing and maintaining it. Or perhaps you are happy with the current level of documentation, noob users support, in which case moving in to the forum environment is probably not to onerous.
Rick has a good point: providing help topics in the forum is definitely less work to do.
Agree administering one site is going to be easier than 2
At the current state of things I would tend to use forum, but naturally, if some has time to provide a well structured wiki page I could reconsider this.
This maybe happening at the moment imo but that is open for debate.
I do not have time to study different wiki engines and such, so maybe I just do not see some kind of easy solution thou. Also, if someone has a step by step instruction of adding wiki functionality to the existing forum engine, then it could be of great help.
From what I have see software tends to do a forum well or do a wiki well but not both (imo). So doing both well would require the user logging into the forum and wiki independently if they wanted to write in either. (And yes I have looked at
WikiStyle SMF theme. Similarly
SMF Online Manual is OK as a manual and reads as if it was written by a documentation writer with the comments mostly asking for support and being referred to the forum, not suggesting updates to the help pages. This is a perfectly reasonable approach if if one person wants control of the documentation, it is just different to a collaborative document. Interestingly they run two copies of the forum software and require a separate login for each)